These flip flop socks have a special padding for the sandal thong knitted in. It helps keep the socks in place and cushions your toes from the thong.
Suggestion: If you substitute yarn, find one with some elastic content. Socks have to endure a lot of movement against a solid object and elastic will keep the socks from stretching out of shape too soon.
If you want, reverse the socks to put the stockinette side next to your ticklish tootsies.
The instructions are written for two at a time, Magic Loop circular knitting. But they can be knitted one at a time on circulars or dpns.
Women sizes, measure foot at widest part: Small, 7” (17.5 cm); Medium, 8” (20 cm); Large, 9” (22.5 cm)

Happy Feet, Happy Sweet Summer!