Double Crochet Stitches
The first default border is very simple.
The first round after the squares are pieced, put an even number of single crochet stitches across the outside edge of each square, with three in each corner. This is an important step for three reasons: First, you can work over all loose tails on the edges and hide them; second, it puts an even number of stitches across squares that may not have the same number of stitches (more on that in a minute); and third, it creates a base edge for continuing the border work evenly around the afghan.
Regarding the number of stitches per square, it is important to create uniformity at the outset. We get squares sent to us that have anywhere from 17 to 25 stitches on any given side. If we were to simply put one border stitch into each existing stitch, the border would be unevenly distributed. Some squares would be bordered by so few stitches, the square will stretch. Others would be bordered by so many, there would be an unwanted ruffle. You can avoid both of these by picking a number and sticking to it! For a typical 6″x6″ square edge, using a size H-8 hook, I like to put between 19-21 stitches on each square’s outside edge. This means that for squares that have only 17-18 stitches, I double up once or twice, and for squares that have 24-25 stitches on their edge, I will evenly skip a few stitches along the way when putting on the border.
Once the evenly distributed single crochet row is completed, and the last stitch is slip-stitched to the first, then I chain 3 (counts as first double crochet), and double crochet into each single crochet stitch of the first round; when I get to a corner, I double crochet 2, chain 2, and double crochet 2 in the center of the 3 single crochets.
I go around in this fashion, with a double crochet in each stitch across, and dc 2-ch 2-dc 2 in each corner until I’m ready for the last round.
The last round can then be either single crochet in each stitch across, with 3 sc in each ch-2 space in the corner, or double crochet in each stitch across, with 5 dc in each ch-2 space in the corner. Bind off, tuck your ends, et voila!