This diagram shows how to mark and cut your plywood to make your template for the side pieces.

Lay down two sheets of plywood in a square. mark off a point 12 3/4" in and 28 1/2" down from the corner. This is the anchor point for drawing your first transition.

Mark a point 12 3/4" in and 3 1/2" up from the corner below the one you started with. this should be your "pencil point" it should be 64" straight down from your anchor point.

use the board-compass method to draw a 64" radius Arc.

Now mark off where the top of the deck is so you know where to stop in order to leave room in the wood for another template.

Also, mark off another 1/2" to the left of your "pencil point" of flat bottom letting the bottom 2x4 be perfectly level.

Cut this out, with either a jig saw, or if you're skilled with a circular saw set at just the thickness of your wood. When you get done, flip it and trace it on to the other side.