Blew out my felted slipper

I made these felted slippers in 2009. They were for my SO, but for some reason he left them at my house and rarely wore them. This past winter, I reclaimed them. It didn't take long for a hole to open up in the heel.

In a way, I am glad this happened, as I have been contemplating stash busting by making more of these. Now I know that I need to double up on the heels and/or add a sole of some sort.

I've also been contemplating how to fix these or at least repurpose them. Any suggestions?