One of my favorite quilts is a large chevron pattern that I made with layer cake squares. I assembled it using the method of drawing a diagonal line and sewing 1/4" from either side and cutting down the middle. For larger squares, I trim using a 12-1/2" ruler, lining up the diagonal line on the seam. For smaller ones, I have a Quilt in a Day Triangle Square Up ruler. With this ruler, you leave it folded, line up the seam and trim 2 sides before pressing it open. It is quicker and less stress on my hand by doing half of the cuts. I frequently make half square triangles, so it was a worthwhile investment for me. The 12-1/2" ruler is very practical to have also. Shop around. I've gotten rulers at very reasonable prices on ebay, as well as some online quilt shops.