I make my blocks slightly over-sized and then after all my blocks are made, I will square them all up.
f the block has a lot of componets, ie. hst, squares, or flying geese, etc. I will square them up as I go, then square up the final block when the block is all put together. Then when I put the blocks all together, my blocks are easy to match up the seams/edges. I don't square up the final full top, as I QAYG and have no need to. Once my blocks are together and the rows are together, my top already square.