Sarah H. answered 07/09/24
High School Science Teacher specializing in Bio and Env/Earth Sci
I will admit that I don't have much experience with crochet (just knitting), but typically when a pattern doesn't say how to attach a piece I choose a method depending on the type of seam. Is the hood something you have already constructed and just need to sew on, or is it a piece you will be building as you go?
For sewing on, typically mattress stitch is the simplest solution, especially if there is a selvedge row for you to sew into. For picking up as you go, you would need to start on one side of the back neckline and pick up each stitch as you come around to it. Sorry I can't be more specific than that without seeing the pattern, but hopefully that helps or at least gives you ideas of what to look up on YouTube!