These are a huge hit in our family, I pretty much make them every year or two for everyone I know, since everyone loves them so much they wear them out in a year!
You can find the pattern here: Fiber Trends Pattern
(sorry you have to pay for it… copyrighted!)
Last year, for my dad who goes outside a lot, I took apart his ripped old slippers with an intact durable outdoor-friendly sole on them, and sewed that sole onto my felted clogs. Worked great, and he loves them! (see top picture)