Optional: Work one or two rounds of Single Crochet before beginning the edging. The instructions say to work into next 3 sc - if you have not worked the base round(s) of single crochet, then you will just work into the next stitch on your item. Try to space as evenly as you can, but don't worry if you have to maybe skip an extra stitch or only skip two stitches between picots to make it fit. It doesn't have to be perfect!
Multiple of 3
Ch 1, 1 sc in next 3 sc * ch 4, sl st in first ch, 1 sc in next 3 sc*. Repeat from * to end, fasten off.
This is a fun border to add to knit or crochet items. It can be awkward at first, but with practice it will become easy.
Reverse Single Crochet or Crab Stitch is worked from left to right, instead of the normal right to left direction - if you are right handed. If you are a leftie, you can find some info here that may be helpful.
Make sure the front side of the item you are working with is facing you, and starting a few stitches from the left most corner, insert your crochet hook and pull the yarn through. Chain one. (This is my personal preference for starting the Crab Stitch. You may begin right in the corner if you wish, and you do not have to chain one. I just find it helpful to do so. I also find it helps get me started if I work a round of regular single crochet. You can begin working directly on your item.)
If you are planning to work this border with the same yarn you are using for the main body of your project, all you need to do is start working backward after the last row instead of turning your work as normal.
You'll want to insert your crochet hook from front to back. The hook should be pointing to the right. Grab the yarn and being to pull through. As you are pulling the hook through, swing or twist the hook so that it comes out pointing to the left. Be careful not to pull the yarn through the loop that is already on the hook. Now, yarn over and pull through both loops.
You can add a Single Crochet Border to anything, be it knitting or crochet. In my video I am working with a small garter stitch swatch that I knit.
I started a couple of stitches away from my corner, then began working a single crochet into each stitch. The corners require a little something extra to help the fabric lay flat. To work your way around the corners, all you need to do is work three single crochets into the same corner stitch. When you make it back to your starting point, just join the round with a slip stitch into your first single crochet of the round. Cut the yarn and weave in the tails. Or, you can continue working in rounds of single crochet for a wider border.