Rushing Rivulet is a pattern by Cat Bordhi from her New Pathways for Sock Knitters, Book One, that I made for my elder daughter. It's a toe-up pattern, here's the beginning, and the finished pair.
Pour faire l'ourlet en picot, j'ai du le replier et le greffer à l'intérieru de la chaussette, voir dans ces photos l'essentiel des manœuvres à faire.
To make the picot hem, I had to fold it over and graft it to the inside of the sock, see the basic maneuvers in the photos above.