From TheCraftOfClothes Etsy Store:
The Compact Backpack is compact in two ways: the pattern pieces fit exactly into a 105cm/41⅜" x 64cm/25¼" rectangle with zero waste, and if you make the backpack in a very lightweight fabric it will fold down small enough to fit in the palm of your hand.
The backpack has adjustable straps, a front pocket and a zip.
It can be made in a variety of fabrics including denim, canvas, furnishing fabrics, corduroy or nylon ripstop. Lighter weight fabrics make a more compactable bag (ideal for travel), and heavier fabrics will make a stronger, more durable backpack.
Secondhand textiles can also be used, and a whole backpack can be cut from a pair of men's jeans.