I used 2 4x8 sound boards from Home Depot. Because they are not very sturdy, my son build a frame with 1/2 x 2 inch pieces of wood. It is a rectangle around the edges with a large X across the middle. I think he screwed it on the back with screws. Then I covered them with very cheap batting from WalMart, which I stapled onto the framing. It is soft enough to just stick pins in and now I can lean them up against the wall and they have been there for years.