I decided to amend the diagram slightly to allow me to piece the bottom section. If you'd like you're, of course, welcome to applique it.
Print or trace the block diagram onto foundation paper, number and cut out as below.
Important! You have to mirror this diagram.
You'll notice that the narrow top section is not in the photo. I thought I could "cheat" my way through it but I couldn't. So cut that out too.
Attach the non-pieced triangle.
Finally attach the narrow top section.