I made backpacks from old pants, shorts and one shirt for the kids for Eid. I was sewing till the last minute so I only managed to round 6 of the 8 total for pictures after I gave them out.
Here's how I made the backpacks:
I cut a sheet of paper into the biggest circle I could and that determine the size of the packs. At the bottom I cut off a little bit to let them be able to stand up when finished. I used one size circle for the front and back and cut a pattern a bit smaller for the plastic canvas I used to hold the shape. I estimated the length of the sides and divided that in half to make the pattern piece to be cut on a fold. I determined the size needed for the base and made a slightly smaller piece for plastic canvas so I could assemble it without sewing on top of the canvas.
I cut one circle for the front along with a sort of half circle for a pocket, and two for the back, one for the outside back and another as a lining to encase the plastic canvas. I did two of the base as well one for the outside and one to line it.
The long strip for the sides was cut from sweatshirt. I originally planned to put a zipper on top, but ended up not having time for that. I used denim from jeans shorts and a cotton button down shirt for the other pieces on this backpack.
The straps were made from some ribbons that I guesstimated the length for. I would have made them from denim if I had more time. They weren't very substantial.
After I did a few this is the assembly method I settled on:
First, I topstitched to pocket to the front piece, reinforcing the corners.
I turned down the upper edge and stitched it down stopping about an inch away from the pocket on either side to leave an opening.
I took the two pieces for the base a sewed them to the bottom of the front. I sewed on the lining and outer piece to the other side of the base piece.
I sewed the side strip to the front piece, leaving a gap where I topstitched for the opening. I reinforced the sides so it wouldn't pull apart easily
I sandwiched the canvas between the lining and outside back, remembering to place the straps before pinning it to the side strip and sewing them together.
Then I flipped the whole thing right side out
and put it onto a cute model
And I was done!