I just use two sqs. For 2 1/2 in hst use 6 in sqs. For 3 1/2 in use 8 in sqs. Draw an x and sew 1/4 in down each side of lines. Cut in half both ways then on lines. You will have 8 hst and just a small trim up.
I use Quilt in a Days triangle sq up ruler also since it only requires one cut.