If I am doing little tiny log cabins - strips 1/4" finished - I will paper piece. For the rest of them - I precut all of my fabric. The trick is sewing straight and having that blessed scant 1/4" seam allowance. Having everything precut also gives you the opportunity to "randomize" your strips well in scrappy stuff. I recently made 36 log cabin blocks with 36+ lights and 36+ darks using scraps. I feel like a robot at times, but when they are all laid out in combinations that have been pre-approved by me!, the assembly process is a piece of cake. The blocks are square.