I square up at the end making sure the corners are square and then matching up the sides to the corners. Sometimes I have to “ease” in something. With few exceptions over the years they all come out square enough, lie flat and look good. They aren’t for show and after using, it just doesn’t matter to me if one is an eighth or quarter inch off on a side. I just read where some quilter just trims the sides and doesn’t actually square off her quilts. Maybe her piecing is more precise. I don’t pre wash and rarely use starch. I don’t have a stash so all my fabrics are new and I’ve never had a bleeder.