The part about leaving a length of yarn when you BO and 'arriving at the CO sts' to gather them? It sounds like you'll use the tail and thread it through the bound off sts like a drawstring to gather them. If that's the case, it may be easier to leave the sts live, and gather them together. Though later it says to join the CO and BO edges in a circular shape.
You might try contacting the people on ravelry who've done this one and see what they did.