For the third round, slip stitch over to the next chain 2 space, repeat the, 3 double crochet, chain 2, 3 double crochet, chain 1, sequence from the previous round for the chain 2 space corners. In between the corners, in each of the chain 1 spaces you’ll crochet only 3 double crochet and a chain 1. When you get all the way around, slip stitch to the top of the initial chain 3.
You’ll repeat the last round until your square measures the size you’d like it to be.
Here are just a few blanket sizes for reference: Lovey 10” x 10”, Receiving blanket 40” x 40”, Swaddler 47” x 47”, Small square throw 52” x 52”.
If you want to change colors, bind off after you slip stitch, then begin your new color by with a slip stich and chain 3 into any corner space.