This was just a quick half-day job so I didn't really take any photos during the install.

I had lots of depth in the wall above the fireplace so used an Intuitive Design wall box placed vertically.  I cut in a hole behind the TV that was about half the height of the box and then cut a 1-gang box in horizontally right above the mantle behind the BEAM with a brushed wallplate.

The Intuitive Design wall box was pushed inside the wall and down and then secured to the framing so it enclosed the 1-gang box below.  The electrical outlet was installed into the wall box and the wall box contained the excess TV & BEAM power cables + low voltage wiring.

Conduit from the wall box to built-in cabinets allowed me to pull the One Connect cable and place the One Connect box in the cabinet along with the cable box and Apple TV.