This is an instruct-able on making a backpack.
Step 1: Cutting out the pieces.
First you are going to want to cut you pieces. I cut two to 10 and a half by 15 and a half those will be the front and back panels. The bottom I cut to 10 and a half by 5. The sides are 15 and a half long and 4 inches wide you will want 2 and 4 15 and a half by 2 and a half for the straps. In the picture I tried to piece them all together.
Next sew the bottom to the front and back of the bag. And then after that sew the sides onto the bottom. After all this is done you'll want to pin and sew the straps on first pin 2 of the 15 and a half by 2 and a half together and sew along 3 sides. Make sure you pin them on the wrong sides cause I messed up on one of my straps. When you sew the straps on you will want to make sure you do several row of stitches across the top and bottom of each one to ensure it will hold. Do not sew the side up before attatching the straps.
Step 3: Closer
Now comes the matter of closing the bag. I put a velcrow because putting on a zipper would require years of sewing experience,
Enjoy the backpack you've just made.