I learned to wet felt at a Hooked in the Mountains workshop. I immediately thought it would be really fun to combine the technique of wet felting with hooking. Sometimes I do the felting and then just sew it to linen or monks cloth backing. Then I can hook around the felted bits. But I have also discovered that you can wet felt right through the backing quite easily. The only caveat is that it will shrink a bit as you felt. I find that needle felting the wool into place before wet felting helps keep things looking smooth.