I finished the granny slippers!
I think the might need an additional cycle in the washer and dryer, but they look pretty cool.
Pattern: Felted Granny Slippers (Rav Link)
Yarn: Noro Kureyon (colour 183)
Modifications: I made all the squares as per the "plain" square. I also made the 4-round versions to get the 10cm squares specified.
Verdict: It's a neat pattern, clever the way it folds. I liked it. I need to felt these some more though.