First, I marked the points with a water soluble pencil:
Then, I cut out the triangles and tacked them down with Wonder Tape. I love this stuff -- for pockets, zippers, applique -- anything, really.
(wonder tape review).
Next, I lined up all the red/white triangles and seams and used Wonder Tape to hold them down.
Here's another pic of all the triangles taped down and ready to top-stitch! Woohoo!