Thank you so much, everyone! If anyone's interested in making this, it's really easy. I didn't have a pattern. There are four sizes of rectangles and one square.
6.5x2.5 inch
6.5x4.5 inch
4.5x2.5 inch
2.5x2.5 inch
You need the same number of each size, and all in a mix of colors. Then just mix and match.