This is a granny square design for Knit A Square. This one works up really quickly - you can bang out a few of these a day, if you have the time.

You can personalize the pattern by alternating stripes of color around, or even using different variegated colors to make it super colorful. You could also switch up the stitches each round by switching between dc, hdc, and sc. I would not make any stitches longer than dc for the main stitch, to keep it tight and warm for Knit A Square.

ETA: Please note, the website is new but the pattern is the same. Enjoy!