This is made with “vintage” Sassaman fabric on the outside and solid broadcloth for the lining. Layered between all the pieces, including the strap, is fusible fleece. There are two pockets sewn into the sides/strap for cell phone, camera, whatever.
Using denim or duck lining would add extra durability and stiffness. Using patchwork for the front and back would look great too. A very customizable bag. Totally easy. Totally cute.