I'm having so much fun making these, I wrote up a simple tutorial. It's a simple and practical project, useful as a lunch or knitting bag. My favorite feature are the french seams throughout -- absolutely no fraying during machine washing!!
* Note: using upholstery weight fabric and stiff cording helps the bag to stand on its own
Upper fabric (cotton): 2 pieces 13 1/2" x 8"
Denim bottom: 1 piece 13 1/2 x 9"
Cotton cording/twill tape: 1 yard
1) Going against most sewing instructions, with wrong sides together, sew the upper fabric with the denim (on the long side). Use a very narrow seam allowance (around 1/8" to 1/4")
2) Trim seam to 1/8"
3) Open and fold with the right sides are together. Press and sew with a 3/8" seam, making sure the previous seam is fully enclosed.
4) One french seam completed. Repeat with the other upper fabric and the other denim side. You should have one long strip with the denim in the middle. Fold in half lengthwise with the wrong sides together and stitch (with a 1/8" to 1/4" seam) starting 2" from the top. Trim seam to 1/8" and press. Sorry for the lack of photos -- I forgot :)
5) At the side opening (created by the 2" opening), fold 1/8" twice toward the wrong side. This forms an opening for the drawstring. Pin, stitch and press. Repeat with the other side.
6) With right sides together, starting at the bottom point of the opening, sew a 3/8" seam capturing the previous seam. Repeat with the other side.
7) At a bottom corner, pull fabric until the side seam and bottom "seam" meet. Sew perpendicular to the side seam, 1 1/2" from the triangle tip. Repeat at the other corner. This creates a flat bottom.
8) At the top of the bag, fold 1/4" and then 1/2" to create a casing for the cording. Pin and sew around. I like to place the cording inside while stitching -- I never liked doing it afterwards. You can use a zipper foot or move the needle position to the far right.
9) Knot and trim the cord ends. To close, pull the cording from both sides. My cording is really stiff -- a thicker version of those strings/ropes (???) to open and close drapes. To allow for shrinkage, have the knotted end an inch wider than the bag.
All finished :)