Get the wing clipper ruler. It gives you instructions for making them from 1" x 1/2" (finished size) all the way up to 10" x 5" (finished.) The method outlined in the book is not that of the author (Joan Ford) but by Deb Tucker (and she states that in the book). Deb Tucker makes and markets a lot of specialty rulers for commonly used shapes, including the wing clipper. Definitely worth the investment if you make a lot of FG (or want to). The method is practically no waste (you trip down with this method but in some cases you are only taking a small sliver off). I am a big fan of Deb Tuckers Studio 180 specialty rulers. I only have a few but I wouldn't hesitate to buy one for a special project. Edited to add, I found a .pdf file on line of the wing clipper instructions so you can see they tell you how big to cut the squares for each size.
https://cdn.shopify.com/s/files/1/12...62701526429277