Thank you Kalle and Jitterjames,
the first one I made I used a three gang box like
this one and used six neodymium magnets to hold the tablet in place and I wasn't quite happy with the price and look when I took the tablet off the wall.
so when I reduced the amount of magnets I needed something to stop the tablet from sliding down the plate, although the tablet never fell off the wall it would slide down until the magnets where at the top of the metal plate on the tablet, so you could see the top of the wall plate. hence the foam pad (cupboard liner) I had some left from a shop project but it was black so I tested it and bought white when I knew it would work.
with my first build I was able to use
1/2 inch ENT Conduit (because I had the walls stripped down to the studs for our remodel) so I could replace the charger cord with ease... but it's a major pain to use it with an old work box, so for now I don't have one for this wall mount until I remodel the hallway where the second wall mount is installed
at some point I'll need to put my video together from our Living room remodel
, I was smart enough to do a brief before, during and after video so I could make one, but got side tracked and forgot about it until I made this video