WARNING: Machine sewing is definitely required for this project. You will most likely be sewing with thick material, so make sure the machine you are using can handle this!
Step 1: Materials
*An old pair of pants or shorts with back pockets INTACT
*A sewing machine
*Crochet hooks (to use as a sewing guide)
*Buttons (if not already supplied on the garment)
Step 2: Cutting Up
I recommend using a zigzag stitch around the cut fabric edges. This will keep the fabric from fraying.
Step 3: Pocket Detail
I made small slots on one pocket to hold my small hooks, and larger slots on the other pocket for my big hooks.
Using chalk and/or sewing pins, mark the areas you plan to sew. After pinning, try sliding a crochet hook into the slots. They should slide in and out easily without falling out on their own.
Now for the sewing. If your pockets have pocket flaps, safety pin them up and out of the way. This will help a LOT while sewing!
Take your time sewing, especially if you have thick material to work with. To make sure the tops of the slot seams would last, I backstitched over them several times.
The picture below shows the backside of the pocket so you could see my stitching.
Step 4: Creating the Bag
Next, match the pockets right sides together and pin the sides and bottom. This will create the main bag.
Sew the sides and bottom, using a quarter inch seam allowance. I also zigzag-stitched around the edges a second time.
Turn inside out. If necessary, press edges with an iron.
If your pockets have a buttonhole, you can add a funky button closure for your pocket.
You can also add a strap using leftover fabric.