X Gantry Leveling Blocks - Ender 3 (or similar)

UPDATE 4/28/2019

So after some more time and much learning, I have made some minor tweaks for better results using different nozzle diameters. Now I have added two different heights for even layering with a given nozzle diameter.

111mm tall block (for sitting on frame) using 0.8mm Nozzle @ 0.6mm layer height
112mm tall block (for sitting on frame) using 0.4mm Nozzle @ 0.32mm layer height

10% infill should be plenty, especially if you use 2 perimeters with the 0.8mm nozzle, or 3 perime