Joan in AK

Eddie had a quilt on here a couple of days ago using a layer cake. It was hourglass blocks with a border. It looked so pretty that I wanted to make one and had a KT Kansas Winter layer cake. For my practice hourglass block , I used 4 of the 10" squares. I do my block this way: I laid light on dark, sewed 1/4 inch on each side of the diagonal, cut down the middle, pressed to the dark side. I put one half square triangle block on top of the other, light on dark, dark on light, drew a diagonal line perpendicular to the seam, sewed 1/4 " on each side, cut open and pressed- one hourglass block. When I squared up my block, I didn't set the ruler right, and my block is off. I had the diagonal line of the ruler on the diagonal line of the block, but something else wasn't set up right. Hope someone can help.