ROUND 1: Pull up a loop in any corner and chain 3. DC around the entire blanket, working 3 DCs into each corner stitch.
ROUND 2: When you reach the corner you started with, work 3 DCs into the corner, then go around the blanket again, this time alternating front and back post double crochet. A front post DC means you insert your hook from front to back around the post of the next DC and work your DC. A back post DC means you insert your hook from the back to the front and work a DC.
When you get to the corners of this row, you will want to continue the pattern of alternating front and back post double crochet, but you will work three stitches around the corner post.
So, for example, if you get to the corner post and you are supposed to work a front post DC, then work a front post DC, a back post DC, and a front post DC all around that corner post. Then in the next stitch you would continue the alternating pattern, working the opposite of whichever stitch you just used (in this example, you would work a back post DC).
Just remember that you are always alternating front and back post double crochet around the whole blanket, you just happen to be working three of those stitches around the same post when you are working the corners.
ROUND 3 – 4: When you finish row 2, work 3 alternating front post/back post DCs into the corner you started with and repeat row 2 two more times around the blanket, until you have four rows total. (Or you can go around as many times as you’d like to get your desired border height. I only had enough yarn to go around 4 times.)
Watch video below for help