This pocket bag process is utilized in the making of a pair of Third Born Sun Day Shorts, but the process can be incorporated into so many of your favorite patterns whether they are pattern hacks, or future self drafted patterns. The same technique is used to add pockets to the side seam of the Sun Day Dress hack (about 3.5 inches from top of top dress tier).
Cut 4 pocket bag pieces. Make sure to note right and wrong side of textile if your fabric as a face. In this case the textile has a subtle twill on one side indicating the right side/face of the fabric.
Serge (or zig-zag) the raw edges of the CURVED SIDE ONLY of all 4 pocket bags SEPARATELY.
Place one pocket bag per front shorts piece at pocket notches (placing right side of pocket bag to right side of short). Make sure you have one left and one right front short as indicated in picture below. Do the same for back pocket shorts.
Stitch pocket bag to short at 3/8'' seam allowance (make sure to back-tack at beginning and end of stitch line). Then finish raw edge of side short piece/pocket piece with serge or zig-zag stitch. Do this for all four side seams separately.
Press pocket side seam flat, then press to side as pictured below.
Under stitch 1/8'' from edge of pocket bag side seam securing pocket bag to seam allowance.
Understitch all four pocket bags separately as depicted below (make sure to back-tack at beginning and end of stitch line).
At this point you should have one left and right back short piece with a pocket bag attached, and a left and right front short piece with pocket bag attached.
Pin right sides together of one front short to one back short (make two sets).
I like to match pocket seams together marking the "pivot point" very precisely as depicted below (this small step helps make the side seam line up nicely).
This pin where you carefully inserted the pin tip indicates the pivot point (do the same process on the lower end of the pocket seam (make sure pocket lays nice and flat).
Stitch side seam of shorts with front/back shorts pinned together at 3/8'' seam allowance (prepare to stop at pivot point pin).
At pivot point, leave your needle shorts, lift up machine foot, and turn shorts. Continue stitching around pocket bag at 1/4'' - 3/8'' seam allowance.
You will travel around the entire pocket bag and stitch to second pivot point.
Leave needle in second pivot point, lift foot, and pivot shorts. Continue stitching down seam allowance at 3/8'' seam allowance.
Press pocket bag flat.
Press seam allowance and pocket bag towards front.
Optional step: secure top and bottom of pocket bag at "stress points". You can do this by stitching 3-4 stitches back and forth a couple times (or using a small zig-zag stitch to replicate the stitch of a "bar-tack machine". You will often find bar-tacks at stress points on your denim/jean garments.
I simply used 3 stitches, went back and forth a couple times trying to make it nice and clean.
For additional strength, you can pull the threads to the inside of your shorts and tie off in a square knot (right over left, left over right).
You now have a side seam pocket!