I will warn you: these are a little addictive to make (maybe because I keep using food-related fabric?).
If you are up for the temptation, you will need:
one 10.5" x 3.5" piece of ripstop nylon (or liner of your choice)
one 10.5" x 3.5" piece of cotton fabric
one 2" piece of velcro (poky and soft sides)
Fuse wrong side of fabric to wrong side of nylon.
**If using a directional print, turn it upside down and keep velcro at top.**
Finish opposite short end (serge or zigzag or bias tape, as in this tutorial). Sew poky velcro 1" down from finished edge and centered on the fabric.
Starting at the bottom corner, serge (or otherwise finish) around the snack sack, ending at the other bottom corner. Fray check ends of stitching.