To Lisanne (and everyone),
I started using a template, copied from The Quilter's Guide to Rotary Cutting that I got from my library. But then I learned exactly how to cut these diamonds using a rotary ruler & cutter. The diamonds are 2 1/4 inches - which includes 1/4-inch seam allowances. The instructions weren't very clear how to cut out the diamonds from the book (I probably wasn't reading it closely enough) but I found great directions online. Maybe my next quilt will be a striking 2-color quilt.