For me, it depends on the size of the blocks. If they are 4" blocks, I assemble them in units and then square up the units at 8" and again at 12". If I had a 16" square ruler, I would go up to that size before I set them into rows. My 6" blocks get chunked into 12" units and squared before making rows. Narrow rows can easily become distorted and the curves get compounded so fast. Squaring up bigger units is added work, but the end result is so much better, at least for me.