If you're curious how to crochet on flip flops, this post will answer all your questions including if they fall apart over time. Great free tutorial on how to get started crocheting shoes and boots for spring, summer, fall, and winter.
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