If you are looking for perfection and don't want to over cut your pieces to square up after, then starch the heck of of them before using, then place a tiny dab of Roxanne glue at all strategic places before sewing. There are videos on this. Also understand that many sewing machines don't pull the top and bottom fabric evenly, so you have distortion there. Starching helps this, and the dab of glue fortifies it.