The Underwater Stripes Bag

I am super-excited to be guest posting today for the Festival of Half-Square Triangles! Megan has put together a really inspirational series (with super great prizes!), and I am really happy to share with you a pattern for a great bag with zig-zag detailing!

This bag is appropriate for a confident beginner, both at quilting and at bag construction. Also, if you have never used interfacing before, this pattern will let you try out a couple different kinds of Pellon interfacing (and types that I use very often in my bags!). Don’t let the zipper scare you! The exterior and the straps are all quilted, and it also features darts as well as an interior pocket.

For my bag, I used Robert Kaufman Kona solids in Turquoise and in Pomegranite. I know there are so many great prints out there, but sometimes using solids can make a bold statement!


Printable Instructions and Pattern Pieces

Finished size: 15″ x 9-3/4″


– 1/2 yard each of 2 different fabrics for the exterior
– 1/2 yard interior fabric
– 1/2 yard Pellon#TP971 Thermolam Plus fusible interfacing
– 1-1/2 yard Pellon SF-101 fusible woven interfacing
– 12″ zipper
– fabric marker or chalk
– ruler
– zipper foot

From the Exterior Fabric

1a. From your 2 exterior fabrics, cut them each into 3-1/2″ strips along the width of the fabric (you should cut 4 strips each fabric). Cut those strips again by 3-1/2″, so you will end up with 48 squares (3-1/2″ x 3-1/2″) from each of the 2 fabrics. These will be referred to as Fabric A and Fabric B.
From the Interior Fabric

1b. Using the Main Panel pattern piece, cut 2 each on the fold for the Interior Main Panels.
1c. Fold your Main Panel pattern piece on the dashed line. Cut 2 each on the fold for the Pockets.
1d. Cut 2 pieces, each measuring 1-1/2″ x 3″. These will be tabs for your zipper and will provide your top zipper seam with a nice, clean finish.
From the Pellon Thermolam

1e. Using the Main Panel pattern piece, cut 2 each on the fold.
1f. Cut 2 strips, each measuring 1″ x 30″, for the Strap Inserts.
From the Pellon woven interfacing

1g. Cut 2 strips, each measuring 3-1/2″ x 30″.

1h. Using the Main Panel pattern piece, cut 2 each on the fold.

1i. Fold your Main Panel pattern piece on the dashed line. Cut 2 each on the fold.

2a. Take your Fabric A squares. Using your ruler, draw a diagonal line straight across the square with your fabric marker or chalk. Repeat for all Fabric A squares.
2b. Place 1 Fabric A square on top of 1 Fabric B square. Sew a line of stitching that is 1/4″ to the left of and 1/4″ to the right of the line that you drew. Repeat for all squares.
2c. Make 3 piles of sewn units. 12 will be used for the straps (set aside for now), 18 for the front of the bag, and 18 for the back of the bag.
2c. Cut all of your sewn units down the drawn line.
2d. Press the seams toward fabric A on all of the sewn units. Trim your squares so that they are each 3″ x 3″.
2e. For the front of the bag, take your units and lay them out. Sew them into 5 rows using a 1/4″ seam allowance (each row will have 7 units). Press the seams open.
2f. Sew all the rows together using a 1/4″ seam allowance. Press the seams open.
2g. Repeat Steps 2e. and 2f. for the back of the bag.
2h. Fold the pieced unit for the front of the bag in half. Using the Main Panel pattern piece, cut on the fold. Repeat for the back of the bag.

2i. For the straps, divide the remaining pieced units in half.

2j. Take 2 units, and place them right sides together as a mirror image. Sew along 1 edge using a 1/4″ seam allowance. Press the seam open.
2k. Continue adding pieces in a long row until you have finished off the half allotment of units.
2l. Repeat Steps 2j. and 2k. to assemble the 2nd strap.

3a. Take 1 pieced Exterior Main Panel and a one of the corresponding pieces of Thermolam. Fuse the Thermolam to the wrong side of the Exterior Main Panel using manufacturer instructions. Repeat for the remaining Exterior Main Panel. At this time you may quilt the Exterior Main Panels if you choose.
3b. Take 1 Pocket piece and one of the corresponding pieces of fusible woven interfacing. Fuse the woven interfacing to the wrong side of the Pocket using manufacturer instructions. Repeat for the remaining Pocket, both of the Interior Main Panels, and both of the straps.

4a. Fold 1 Strap in half along the long edge. Press. Fold the bottom long edge of the strap up 1/4″. Press. Also fold the top long edge of the strap down 1/4″. Press. Repeat for the remaining strap.

4b. Open up 1 Strap and place the Strap Insert inside. The insert should settle nicely in between the pressed creases. Repeat for the remaining strap.

4c. Fold both straps back together and press to fuse the Thermolam in place.
4d. Topstitch along both long edges, 1/8″ from each edge, of each of the straps. If you choose to do so, you may also quilt the strap.

4e. Take 1 Strap and 1 of the Exterior Main Panels. Measure and mark the top of the Exterior Main Panel, 1″ in from the left-hand edge. Do the same for the right-hand edge. Place each end of the strap to the inside of the marks that you made. Make sure that the Strap is not twisted. The raw edges of the Strap should be even with the raw edge of the top of the Exterior Main Panel. Baste in place with a 1/4″ seam allowance. Repeat for the remaining Strap and Exterior Main Panel.


5a. Place the 2 Pocket pieces, right sides together. Sew along the straight top edge only. Press the seam open.

5b. Turn the Pocket pieces so that they are wrong sides together. Topstitch along the edge that you sewed in the previous step, with a 1/8″ seam allowance.

5c. Take out 1 Interior Main Panel. Place the curved raw edges of the Pocket even with the side/bottom raw edge of the Interior Main Panel. Pin in place. Baste the pinned edge using a 1/4″ seam allowance. Also finger press a crease down the center of this Main Panel. Sew down the creased edge, on top of the Pocket only. This will divide your pocket area in half.


6a. Take out the Main Panel pattern piece. Using 1 of the Exterior Main Panels, transfer the ‘V’-shaped dart marking onto the left and right half of the Exterior Main Panel (the wrong side of the fabric) using your fabric marker or chalk.
6b. Pinch the left-hand corner of the Exterior Main Panel (the right sides of the fabric should be touching). Check both sides to make sure the marks line up on both sides. Pin. Stitch down the line that you drew.
6c. Trim the seam allowance with your scissors, to approximately 1/4″. Press the seam open.
6d. Repeat Steps 6b. and 6c. with the right-hand corner of the same Exterior Main Panel.
6e. Repeat Steps 6a. through 6d. to sew darts onto the remaining Exterior Main Panel, and both of the Interior Main Panels.


2a. Take one of your 1-1/2″ x 3″ pieces. Press in half, right sides together, so that both short edges meet. Press. Fold the top of the fabric down to the crease. Open out again, then fold one edge in to meet the crease and press. Repeat with the other side. You should have created a tiny piece of double-fold bias tape. Repeat for the remaining 1-1/2″ x 3″ piece.
2b. If needed, trim your zipper so that it is exactly 11″ long (including the zipper tape; do not cut the zipper end off or the zipper itself). Slide one end of the zipper in between your pressed fabric, with the end of the zipper hitting that center crease. Pin in place. Topstitch the fabric 1/8″ from the zipper. Repeat for the other end of the zipper and the remaining piece of bias tape.
2c. Trim the excess fabric on either end of the zipper so that it is the same width as the zipper. 
2d. Place 1 of your exterior pieces right side up. Take your zipper from Step 2c. and align it with the top, 1-1/2″ in from each side edge. Pin in place. With your zipper foot on and using a 1/4″ seam allowance from the top of the bag, stitch the zipper in place, including both zipper tabs (you will be sewing on top of the straps).

2e.  Place 1 of your interior pieces right side up.  Place your exterior piece right side down onto the interior fabric piece, with the zipper at the top. Pin in place. Sew directly on top of the stitching from the previous step (do not sew the initial or ending 1/2″).

2f. Repeat Steps 2d. through 2f. for the other side of the zipper. Remove the zipper foot from your machine.
2g. Unzip your zipper at least halfway, so you will be able to turn the bag right side out at the end. Open out your fabric pieces so that the exterior pieces and interior pieces are both right sides together on either side of the zip, and pin in place. Starting at one end of the zip on the exterior fabric side, stitch around the edge of the pieces, pivoting at each corner, and finishing at the zip on the other side. Do not sew on top of the zipper tabs.
2h. Repeat for the interior fabrics, using a 5/8″ seam allowance, and ensuring that you leave a 6″ opening along the bottom. This will enable you to turn your bag right side out and for the interior to fit snugly inside.
2i. Turn your bag right side out through the opening in the interior. Either fold the opening in 1/2″ on each side and topstitch closed, or slipstitch the opening closed by hand. Press the bag well for a nice, finished look.

CONGRATULATIONS! You’ve finished!!

If you have any questions about this pattern, feel free to e-mail me directly at, or check out my Flickr Group! I would love to see your completed project posted there!  

32 thoughts on “The Underwater Stripes Bag

  1. This looks like it could be sewn up and finished in a day! I still want to make the Frou Frou, but I think I will give this one a try today as it looks quick. The Frou Frou will have to wait until I have more time.

  2. Love this idea. Thanks for all the tips in the tutorial too. Chevrons are way popular right now.

    Just finished a project for a charity event to raise money for the the local food pantry. You’d really like it.
    Mary Fioretti

  3. Great looking bag! I would love to give this a try. Your tutorial was super, easy to understand and lots of pictures. Thanks for sharing!

  4. I like the style of this bag. Your instructions are easy to follow. I am a quilter but want to expand my sewing craft. I have not made a purse/bag yet and this one looks easy and stylish. I will need to get fusible batting first. I will let you know how it (they) turn out.

Comments make my day and I love to reply!