This is a nice one because you really could add this pocket to any pattern.
1/2" double-fold bias tape (I like to use a contrasting color to add a little spice.)
1. Cut out the pocket. (Pattern is below.)
6. Fold down the corners of the bias tape casing toward the back of the pocket so that the side edge meets the bottom edge. Stitch in place. (This keeps the edges from peaking out on the finished pocket.
Tah-dum, you are finished!
Here are the patterns for the pockets. One is a size small (up to 2T-ish) and the other is a size medium (2T to 5ish). Click on the pictures below to download the patterns. You will need Adobe Reader to do so. It's free, and you can download it here.