The instructions I've seen start with 5 squares all the same size. Wouldn't you just use a larger square for the center? I would just experiment with some 'what was I thinking' fabric'. Start by using a center sqare 1" larger than the outside squares. If you use a long stitch length, you can easily remove your stitching & reuse the patches. Then just keep adding 1" to the center block until you achieve the look you are going for.