This board is made from a piece of acrylic and the back doubles as a light reflector when I'm taking photographs. You can use any surface that is flat. This board is A3 (420mm x 300mm) and easily fits 4 different grades of sandpaper, each is a little smaller than half a sheet. You can use odd shaped bits, they don't need to be uniform. Taping down all the edges of the paper is important to give a sturdy surface that doesn't move around. I use masking tape or painters' tape to secure the sandpaper to the board so I can write down the grit number.
My board is A3 size and has room for 4 different sandpaper grits.
Tape down all edges of the sandpaper so you get a sturdy surface that is easy to use.
I use painters' tape so I can write down the grit number.