I would cut the hst's slightly bigger than they're supposed to be, cut a long strip of the centre, and sew the big trianlges down one side, the little triangles down the other, then cut the block sections apart and trim to size.
Not sure if that makes sense, but it's the same way the lattice quilt is made, and it's very quick. The lining up is easy, because once you've sewn the triangles down one side of the centre strip, and ironed them open, the triangles for the other side get placed face down so they sit on top of the bigger ones and you can line them up easily by eye.
:-)