Use a diamond shaped cutter if you have one. Or make a template from cardboard and cut the diamonds using it.
yes get a diamond cutter. a square turned side ways isnt a perfect diamond shape. there are various sizes available too.
or take a square cutter you don't mind permanently changing and pinch two opposing corners together to make it into a diamond shape.
PM me if you want more help.
Thanks! Obviously I have never noticed diamond cutters before. I'll check it out...it would make my life so much easier!