How to fasten off in crochet
Once you’ve finished your last stitch, fasten off and cut the yarn to make a tail.
How much yarn should you leave? It depends. If you’re planning to hide the yarn tail, which is called weaving in the yarn tail, leave enough so you can comfortably thread a needle and weave in the tail. If you’re going to join this piece to another, leave enough yarn to do that and weave in the remaining tail. The way you weave in the yarn tail depends on if you're finishing a flat piece, or a round closed piece.