please ask in a sentence what you need ideas on.
If you can sew then I would get some fleece( make sure it's not too fluffy, test by pulling some of the Tufts on it . If they come out don't buy for a baby, you don't want them choking on fluff). Then turn edges in and either blanket stitch around or machine stitch around.
If you don't sew then cut strips around the edge of the fleece. Measure 10 cm in from each corner then cut out the square. Cut approximately 10 cm up towards the middle by each strip 2 cm wide. Then knot each one to the next one along until you reach the corner then start the other side. Do until all side are complete.
Buy a pattern Crochet or Knitting and some wool and get started, or cut down a Blanket and Blanket stitch the edges or add a biased trim edge.
here's an idea from hometalk: