So I got a little impatient, but finally figured out how to share these squaring instructions with you. So here we go.
Layout the QST block as shown. Place the ruler on the diagonal seam. Look at the bottom right edge of your ruler. The edge of the 4 1/2" line on your ruler should be touching the seam of the quarter square triangles (for our purposes in Paddle Wheel, use the 2 1/2" line. ) Now trim the right and upper edges. Turn the unit 180 degrees and measure the finished size, in this case 4 1/2", but in our case 2 1/2". Trim the right and upper edges again.