When attach hair for Amigurumi dolls,there are many different styles and techniques to do.For me I like something easy and fast.So I used a small book or you can use a piece of card board to hold yarn together it depend on how long of doll hair you want.
Then cut it one side.
Then we divided yarn into many groups and tight it up.
Then we sew it on the doll head by used similar color of thread or
yarn but before that we should put doll eyes first because you can know
and adjust the position of the hair.
Finally,adjust hair style and trim hair to make it look tidy.