Cut off one leg, just below knee, with adult size pants, about 40cm.
Prepare your belt by cutting one strap of about 10 cm, buckle included and still attached another strap of about 40 cm, starting to measure from the other extremity of the belt so this part has the holes two strips of about 3cm, each.
Turn the leg inside out. Since the bottom seam will become the top of the bag, we will close the other end. Insert the belt part with buckle, at that end, making sure it's positioned right in the middle. Close the seam, and run a zigzag stitch to prevent fraying.
Make boxed corners as shown. Attach the other strap, nicely centered in the back.
To make the sewing easier, prepare the leather by making holes using an awl. Next, add the short strips with a couple of stitches. And that's it! Hope you like it...