Here's my template for making a square shaped yo-yo. It will fit on a 6" square, making it perfect for using up scraps or charm squares. Finished size of the "Squareyo" is 2.5". You'll need a lot of them to make a coverlet.
Begin by folding the 4 flaps toward the center, right sides of the fabric together, and sew the edges where they meet, making a pyramid shape. Leave the blunt edges of the "points" unsewn, so you have a little hole in the top of your pyramid. It should look something like this.
Fold the top edge of the opening down and make small running stitches that you can gather up later. Do not knot your thread at the end.
Turn the Squareyo inside out and arrange the shape. You can now gather the threads in the center of the square, and tie them off. Make a few thousand of these, and assemble them side by side with small stiches.
You do not need any batting or backing for this project. Really.