I have not yet made a log cabin, but have read several posts over a period of time that said if you don't cut the strips to the exact size, the blocks won't be as accurate. I was surprised by that. I just assumed if you were careful, you could sew and trim and get a nice block. I read a post on another forum where someone made the whole quilt by the faster, sew and trim method, and the quilt was way out of square. I guess she didn't square up after she sewed the blocks.