If you use a paper template with the seam allowance marked exactly, you just line up the 1/4" on your ruler, with the seam line and cut. Doesn't matter if you trim a sliver off the paper template if you're always lining you the 1/4" line on the seam line. I use a paper template for my Big, Easy Dresdens. It seems to work better for me than drawing lines with a template, which adds the width of the pencil lead or pen. With a paper template and rotary cutting, I can accurately cut up to 6 at a time. If the pieces are all the same width, you can start with a pre-cut strip of fabric. That reduces two sides that you have to cut with the template.