Was when a quilt teacher told us when sewing a sq in the corner on a bigger sq to make a half triangle to start at the point like normal but gradualy sew a liitle off your line along side and go back to the point.Make sure this is on the side where the point is so whren you press over you have the extra.
THis gives you a little extra to fold back and then you can sq agin and not be short.
Clear as mud. lol
Gale