The white square on the left is wash-away foundation with the pattern printed on it.
Piece both squares, making sure to nest the seams and open up the intersections on the back of the smaller square, and cut out the small square space from the wash-away foundation.
Iron the foundation to the back of the large square.
Cut away the inside of the opening, leaving a quarter inch allowance. Cut at the corners right up to the point, then glue the edges to the wash-away foundation using basting glue.
The small block is centered evenly over the opening.
Carefully line up the blocks, pin and hand sew the edges exactly as you would for reverse appliqué.
After trimming with the Dear Jane Square, I'm happy with the results. Both blocks look symmetrical, lines are straight, and points are relatively pointy.