Step 2: Preparation
The type of media boxes I'm using are the only type I could find locally, and they were only available in white. I didn't want any white behind the TV, I thought it would catch the eye when viewed at an angle. I purchased some Valspar plastic paint, gloss black. I separated the face plate on the media box, taped off the bristles, and followed the instructions on the can (wait 24 hours for full cure, so this had to be done in advance).
There was a slight texture to the plastic, so the paint shows this texture, but I don't mind because it'll be mostly hidden from view. If I wanted a very glossy look, it would have been easy to sand it down. Any scratches in the paint during installation I touched up with a black Sharpie. Cheap, but again, it will be mostly hidden from view.
Also for preparation, before removing the TV from its mount, I taped off where the corners of the TV were on the wall. This allowed me to quickly see where the edges of the TV were, without having to make a lot more measurements once the TV was removed. Not seen in the photos, I also marked where the hooks on the TV were located on the mount itself (low-tech method of dabbing my finger in the accumulated dust). With these reference points, it was easy to locate the best spot to place the media box, so the HDMI cable would run directly into the desired input port on the back of the TV from the wall.
I also marked the best spot for the power outlet. I knew my TV tilted forward, and the power plug needed a few inches of space once plugged in, so I located it above the bracket where there would be enough space. A recessed power outlet could also be used, if more space is needed for the plug.