If you are joining an international group, you need to know that you can NEVER match their measurement if they are using metric. You can NOT make a 23" 9 patch. You can cut your squares 8.5" and end up with a 24" finished 9 patch. Or you can cut your squares 8" and then have a 22.5" finished 9 patch. I would certainly suggest you find a basic beginning quilt class that can show you thru all the basic skills you will need. Good Luck !!