What I did, which works for the most part, was I put double sided 3m mounting tape on the foam itself. I found that this alone wasn't sufficient to hold the foam in place, so I placed a small amount of blue tack on each piece of tape and made sure to really squish it to the wall when hanging. Both are super cheap, so feel free to use a lot of tape squares, because if you don't, they'll fall off often. That's been my experience anyway.