did a step by step tutorial on how I made mine. Sorry I'm linking to my personal website but it's in my signature already. I'm just not going to copy and paste everything here...
http://yarn-or-fabric.weebly.com/1/p...sign-wall.html
Sall - I don't think the foam insulation boards are rigid enough unless you are going to be able to store them flat. They will sag if they aren't stored flat. You'll be able to lean them up against a wall when you use them but I'd suggest storing them somehow where they won't warp/sag.