I dont make them that large but you can make 8 at a time by using two 14inch squares, draw an x. sew 1/4 in down both sides of lines. Cut in half on both sides then on drawn line. You will have 8 triangles that will only need a scant square up.
This method is El Burns way. For each size squares needed you add 2 inchs to the size of the two squares. So a 2 1/2 inch you use 6 in squares, for 3 1/2 use 8 inch squares. I also have the triangulations cd but it was expensive for what you get.
But it does make exact size HST.
I highly recommend Quilt In A Days triangle square up ruler, it saves so much time when squareing up HSTs. One cut.