This is an extremely simple way to keep you patch kit snug in place. It is basically a pocket and a flap measured to specifications.
Step 1: Place Your Patch Kit on the Denim
Place your kit on the denim and determine the amount of denim you need plus about 1/4" of space for sewing. Cut the denim out and use that as a template to cut the other side.
Step 2: Place the Denim Together
Place the two pieces together. Make sure they are placed with the inside part of denim on the outside. Sew together the two sides 1/4" in on the three sides. The top is left open.
Step 3: Flip Inside Out
After you have sewn the two pieces together, flip it inside out and you have your pocket.
Step 4: Make the Flap
Take another piece of denim that is twice the height of the pocket you just made. It should be twice the height and the same width. Fold the strip in half with the inside part of the denim out. Sew the denim in the same way as the pocket except only sew one side together so it makes a half pocket.
Step 5: Sew the Two Together
I sewed my bag with the flap being 7/8" higher than the pocket. I sewed the flap on the open side straight through the side of the pocket to the other side. I sew this about 1/2 way up so there is free movement to open and close the flap.
Step 6: Add Patch Kit
Now just add all the stuff you measured the bag to fit.