How to finish an open edge with the invisible fasten off
For amigurumi pieces that'll be sewn onto another piece but with the edge still visible, there’s a slightly smoother way to finish the piece. Like the regular fasten off, once you’ve finished your last stitch, cut the yarn to make a tail. Remember to leave a tail long enough so that you can use it to sew this open piece onto another piece.
How to do the invisible fasten off in crochet (step-by-step with photos)
For pieces that’ll be sewed onto another, or for a piece where the edge will be seen, you can use a technique called the “invisible fasten off.” This technique makes the edge look smooth.
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 attach 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 piece crocheted in rows, or finishing a piece crocheted in rounds.