I lay my canvas out (for the roof pieces) as indicated below. Each wall piece is just the true height of the wall plus the ground flap plus seam allowance.
Additionally, I have changed the method I use for the roof "flaps". I no longer use individual roof flaps, but instead have the valance connected all the way around. My experiences with my first two pavilinos that had individual flaps has convinced me that having a single valance is the better method. The image below shows where I cut the "flap" piece to sew them together, without them simply being a true extension of the roof piece triangle.
