I finished "the block". The hard one. The one I simply could not figure out.
What follows is what I did and not necessarily the best method.
One thing I know: try to sew as accurately as possible. Even the teeniest misstep can result in big problems.
Print or trace the block diagram onto foundation paper, number, and cut out the sections as below.
Don't worry about the sharp points of the sections. They aren't going to show.
Cut the kite sections out only along the two seams that face toward the center of the block. Leave ample fabric on the other sides (at least 1/2" beyond the seam lines of the kite).
Sew the four sections into the appropriate areas on the block.
Sew only the two "inside" seams.
Yes, you will have to use set in seams. (Sorry.)
Use these to make four half square triangles.
Sew them together as if you're making a pinwheel.
Cut out the center section, leaving a scant 1/4" seam allowances. Clip the inside corners. (Actually you can just unpick the seams up to the freezer paper edge.)
Place the foundation pieced block section right side up on the table.
Place the "frame" section right side up on top of it, carefully centering it.
Baste through all layers at least 1/4" away from the freezer paper frame edge.
Trim the block to 5" x 5", i.e. 1/4" beyond the freezer paper edge on all sides. Remove the freezer paper.
Cut away any excess fabric from the back of the block.