Use a Square Ruler to Square Up the String Block
Turn your completed string block over so that the muslin foundation is visible. Use a square ruler to trim it back to exactly 8-1/2" square.You might find that your next starter foundation does not have to be a full 1" taller and wider than your finished block size, that you don't lose foundation width and length as you piece. If that's true, cut your foundation about slightly smaller.


