I am on the "hand me down" list of a couple of great "cowboy" types who will give me their old Wrangler jeans when they have seen a little too much time in the saddle. So take an old pair of jeans and cut up the legs of the INSIDE leg seam.
Open the pant leg and trace a pattern from your favorite stocking or use a pattern that you already have. Place the front pattern piece on the right leg of the pants and the back pattern piece on the left leg of the pants.
Make sure that the center of the pattern is on the OUTSIDE seam of the pants and trace and cut out.
Follow the same steps for the back using the left leg of the pants.
Then closely trim out a pocket from the pants. I like to use the one with the tag on it but you can use what ever you prefer.
Then flip the pocket over and remove the inside piece to leave only the stitching and the front piece. This will reduce the weight and bulk of the pocket.
Then pin the pocket approximately 2 1/1 inches from the top of the front piece of the stocking.
Start stitching the pocket to the front piece just below the grommet of the pocket with dark thread in the outside seam so that your stitching doesn't show. Go all the way around the three sides of the pocket and then go to the top of the pocket and stitch just to the left or right of the grommet to secure the top portion. Part of the fabric next to the grommet can be hand stitched later if desired. I leave it undone.
Then pin right sides together matching up seams from the pants.
I use a 1/4 inch seam allowance so that there isn't a lot of bulk inside of the stocking. Seam all the way around the three sides of the stocking being careful of the original pants outside seams. It will be VERY bulky and you will need to take your time to go over it. You may wish to clip the seam allowance on the curves of the stocking to make it easier to turn right side out. Turn stocking right side out and smooth the seams with an iron.
At the top of the stocking trim the seam allowance at an angle to reduce bulk.