I only use the two HST method. The one you're using gets me too confused. Two squares RST as you said. Draw diagonal line, corner to corner, on the back of the lighter one so you can see it. Sew 1/4" from the line first one way then on the other side of the line. These are easy to chain piece. Then cut in two on the line and you have two HST. My measurements are 1/2" bigger squares to start. So.....start with 6" squares, RST, and when you cut apart you should have two 5 1/2" HST finished.