I would probably use treated plywood and put a piece of carpet on top of it (take the carpet out after season so it doesn't hold moisture). Be sure to use either stainless steel screws or double hot dipped galvanized nails. The new treatment process uses a salt based treatment and the chemical will eat up regular nails or screws in a short period of time. I had rather buy metal ladder stands myself, cheaper, safer, and easy to move.