Pattern: "Granny Square 37" from 99 Granny Squares to Crochet from Leisure Arts.
I used cotton yarn and a J hook to crochet this square. It worked up to 7" before I added a single crochet border in blue. I like to make cotton squares like this as hotpads. Even though it is only one layer, the center of popcorn stitches makes it thick enough to protect most surfaces from hot pots and pans.
I usually leave a little chain space in the corners, but for things like this that will not be joined to other pieces, I do like to make the corners more solid. For each round of this blue border, I worked a sc in each stitch along the sides and three sc in each corner, but on that first round, I skipped the first stitch of each side.