With a complicated design like this, I think we need a picture or link.
If you don't have a pattern, what I would do is make a full block for your first setting triangle & starch the heck out of it. Mark the diagonal, then sew a line of stay stitching just to one side of the diagonal. Then cut it. but NOT IN HALF, remember to add the 1/4" seam allowance past the diagonal line. Your setting triangle will have a bias edge, but with the stay stitching & careful handling you should be OK. Use this cut triangle as your pattern for the rest of the settings.