Genius slipper design where you knit a short "scarf", fold and sew onto your bottom. Garter stitch extra chunky yarn about wide, and however many rows you need, then sew into the 2 layers of the felt bottom.
This pattern is for knit slippers, but I can totally see using a wool sweater and cutting and serging slippers from it! Home Slippers - DIY. this is knitting, but I bet I could use this to crochet some