Judy Martin's newer books suggest strongly that you cut lenghwise with the grain and pre-cut lengths. I use this method on square log cabin blocks, because you get immediate feedback if your blocks are not coming out to the expected size. However, this is not the only way to make log cabin blocks, and if another method works for you, then there's nothing wrong with using that method. The quilt in my avatar is a log cabin, but the strips can't be pre-cut to length because the block is diamond-shaped. I had to come up with other ways of making this block keep its size and shape when I was writing the pattern.