Yeah, the whole sandal is crocheted, including the single crochet sole! An ankle crochet chain strap keeps the crochet motif and heel secure.
Notions: St marker (m); one pair of inexpensive flip-flops in proper size with ½” uniformly thick soles and straps removed, in a color similar to twine; sewing pins; metal yarn needle; one 2.8 fl oz tube of 100% silicone rubber sealant; latex or nitrile gloves; adhesive spreader for vinyl flooring (available at hardware stores in the flooring section-a piece of plastic with a handle on one end and a serrated edge on the other. It is used to spread the rubber sealant evenly onto the bottom of the shoe. I used Homax brand 3” spreader with a 3⁄16” tooth).