With the rubber liner removed, there seems to be a lot of air flow coming from that hole, so I closed most of it off by stuffing some cloth in the hole. I think it is intended to be cooling air to keep the phone cool during charging. There is a hole in the bottom of the pocket. The cardboard piece on the back is just there to act as a spacer to take up a little space. The front piece also allows the phone to slide in better than if it were just sliding against the foam, which tends to grab the phone. The purpose of that is to guide the phone into place when inserting it. The one on the front is 1/2 inch longer than the foam and I bent it 45 degrees. I cut out two pieces of cardboard from a breakfast cereal box and glued them to the front and back of the foam. It cost $.77, and there was enough to make 3 or 4 spacers, so if I screwed one up, I could make another. It is black, 20mm thick foam that is used for aquarium filtering. It seemed to work OK if the rubber liner was removed from the pocket, so I then built a foam spacer to put in the rear part of the pocket so that it would hold the phone in place when charging (see pictures). Then I tried a few different cases on my phone, and had pretty good luck with a thin, clear, TPU case. First I tried cutting out part of the rubber pocket liner as described in an earlier post. I had to make some modifications in order for wireless charging to work reliably on my Samsung Galaxy S7 Edge.

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