I never thought of the aluminum foil but I think it is a smart idea! My husband made mine according to the directions we found from plywood with W&N for the batting and then I covered it with a canvas fabric stapled down and then a cute fabric which is duct taped to the reverse so I can easily change it.
However, when I iron in one spot a lot, I start to smell the glue from the wood. I bet the foil would prevent this.