I use Quilt In A Day's method using large sqs to make 8 hst at a time then sq up with the triangle sq up ruler with one cut. Perfect every time and so fast and easy. 6 in sqs for 2 1/2 in --8 in sqs for 3 1/2 in.
Just draw an x on the wrong side of top sq and sew down both sides of lines. cut in half both ways then on lines.
Sq up with their ruler with only one cut.