Two medium sized wonky triangles panels (or any fabric cut to the size you need/want for your pocket)
Interior pocket fabric lining
Sew together two panels (or cut out the size of pocket you want using fabric you would like for the outer pocket). Using your panel as a template, lay it on top of your interior pocket fabric. Cut out a second piece of fabric.
Place both pieces right sides together. Pin into place. Sew along all four sides using 1/4" seam (scant 1/4" if using the wonky triangles pattern) leaving about a 3" opening.
Trim corners. Pull your fabric right side out, and turn your corners. Press flat with a hot iron.
Whipstitch your opening shut. I like to do this even though you'll be stitching it down, so it's a personal preference.
Place your pocket on your bag and pin into place. Sew on the three sides of the pocket onto the bag. I used about a 1/4" seam. That's it!
Need some help with fabric selections? Here are some great fabrics to choose from.