Original post here! I put the slippers around my foot casts (filled with scrap fabric to make them firm) then ran them through the washer and dryer.
Overall, they fit better but there’s still a bunch of extra felt around the ankle. As it turns out, positive molds (vs negative molds, i.e. casts) of your feet are bigger than your feet, so these are a bit loose. For actual shoes or other tightly-fitted footwear, I’d want to do some additional shaping via cutting/sewing. The instructions I followed (loosely) for this project were meant to be boots with a tongue and laces – hence where the extra felt was supposed to go.