Cut a square the size of the straight edge of the triangle, draw a diagonal line on it from corner to corner. Do a stack all at once. Put the square evenly on a corner, sew on the line. Do these the strip method. It goes much faster and cuts down on thread ends. Go back and sew the extra 1/2 inch from the seam so you have the extra little HSTs, if you wish. Cut between the stitching and press.
Does anyone want a stack of litle HSTs in blue with red and white stars and a white solid? The print has some poly and is not soft, but it worked up well in a small amount.