Updated: Apr 21, 2020
I use this fasten off for almost every project so I just want to share how I do it because you may have noticed that it pops up in almost every one of my crochet patterns as well. If you prefer to do it a different way that's totally fine, I have seen other ways of doing invisible fasten offs that also hide very well. I'm not sure where I picked up this technique or even if it's the right name for it but I'll be using this little triangle made of single crochets to demonstrate.
Complete your last stitch and then slip stitch into the next stitch.
Remove your hook from the loop and insert in the next st from the inside (wrong side) of your work to the outside (right side).
Place the loop back on your hook being careful not to twist it.
Pull the loop through so it is now on the inside (wrong side) of your work.