How do you remove stuck down foam layer on a shadow box?

I bought a shadow box, thinking it just had a black background, which is what I wanted. Well, I went to use it and it%26#039;s squishy and is used to velcro things to. I don%26#039;t want to do that with it. So, I removed the %26quot;squishy%26quot; part and am left with a thin layer of foam that is glued down. I got some of that off, but it%26#039;s glued down pretty well. How can I remove it??





What I%26#039;m trying to remove it from is sort of a picture frame back type thing.





Thanks!|||There is a product called Goof Off, it will help you clean off the rest.