Step 1: Design and Cut
When sewing plastic there's no fraying, etc., buy it look nicer if you make some kind of hem. Just fold it in and sew, 0.5 cm would do.
A general tip - this material is a bit more difficult to sew than other plastics. The bubbles tend to get in the way and jam the machine. Sew slowly and punch little holes in the bubbles while sewing.
Step 2: Making the Straps
I usually use a chalk to mark fabrics. Here I use erasable markers. Mark the exact point the strap is attached on the other side of the bag before you start sewing.
I usually sew at least a square shape attaching the straps, here I only made one line, on top of the hem I made earlier. You can use either zigzag or a regular stitch, as long as use go over it at least a couple of times.
Step 3: You're Done!
You can try this with different kinds of bubbles - please post pictures of your projects!