I much prefer not using the folded corner method, however I'm currently doing a pattern that uses it extensively, Dinosaurs by Elizabeth Hartman, and it would be a lot of work to figure out another method. I find that I have to sew just to the side of the middle line, or my corners end up too small. I don't mark, just use the stitching lines on my sewing table (it's a decal that goes over the machine bed). I line up the target corner just over the stitching guideline. I use my regulars ruler to trim off the corners, to leave a 1/4" allowance. So far everything is coming out fine.