This cast off works without the set up rows. The video shows how to start with a purl. You need to cut the yarn strand after leaving about 4 times the length of the hem that you want to bind off. It’s a neat trick to fold the yarn on the needle but you can also thread the yarn on the needle as you would a conventional sewing thread. It’s best to work this bind off all in one go with no distractions.
(The video has no sound.)
It’s a wonderful wrap around bind off that is a lovely finishing touch!