I use old carpet and doormats. I cut them 3 x 3 square with a razor knife and stack them in the loft of the garage.
When I'm ready for it, I glue them together with latex carpet glue. Paint it on, stick them together and then put a board and something heavy on top to dry for 24 hours. Make it about a foot think. Mount on a frame. If you want to shoot broadheads, you just shoot into the side. Works nice and lasts a long time. You use both sides. You can even peel the top 4-5 layers off and glue a few new squares on and it's like new again.
sam