Chain 3, this counts as your first double crochet. Work 2 double crochet through loop. Chain 3. Work the pattern - chain 3 and 3 double crochet - until you have four sets in the loop. Slip stitch to the top of chain 3 (in row 1). You now have your base square.
Chain three, turn, work 2 double crochet. Note: To finish the corner pictured here, I worked 1 more double crochet, chain 3 and three double crochet. In each corner of the square there will be 3 double crochet, chain 3, then three double crochet. Join with a slip stitch at beginning chain. Chain three and turn. To make this a blanket you will just keep going in rounds using this pattern:
3 double crochet , chain 3.
In each corner 3 double crochet, chain 3, 3 double crochet.
Slip stitch at the end of each round, chain 3 and turn.
When the blanket is the size you want it, chain 1, single crochet in every stitch around. If you used the cotton yarn and feel it looks a little wonky, all you have to do is "block" it. I found good blocking instructions HERE . You can now add your favorite edging or run ribbon through the holes from the row, or just do both! I hope you have fun with this old pattern. I will add a picture of my finished blanket in a few days.
I've had trouble lately with my thread getting dirty and "running" away from me. This was my solution: I took an old, small, coffee can, put a hole in the top big enough for my thread to come through, and put the thread inside. Now my thread stays clean and it stays right at my feet while I work.