Yoo: The designs hold up beautifully. The colors do fade some but I'd imagine that's to be expected considering it's being subjected to soap and hot water over and over.
Still: The jist of it; I wet felt the wool on the soap and let it dry. Then I dry felt the wool on the soap (to tighten it up and make sure it doesn't slip/slide). I then pick a design and make a tiny stencil. Using tiny bits of colored wool, I dry felt it with a single needle until it's filled in. It's easy but tedious.
I love it though. I kinda stopped because people weren't really appreciating it as much as the work I put into it. They'd mentioned they didn't really care what design, they were more interested in the type of soap and scent. So I stopped designing them and have kept them solid colors. I will do a custom design if someone wanted it though since I know they'd appreciate it.