Here is a project I did a few weeks ago using a pair of old men’s cargo pants and making a back pack. I used some leather scraps from around the house and a contrasting fabric for the straps and trim. But this afforded me to reserve the other leg for a future project.
First cut up the leg and pocket.
I used the back pocket as in inside pocket.
Sew up the bottom and run a bias of contrast across the top.