There is an existing thread regarding wireless charging but it has no 100% firm details in it so I thought I would start a new one.
You can see the original here:
First off the mod is not for the faint of heart. The soldering isn't actually too bad, ripping the entire phone apart is the ugly part.
I used a charging pad from a Samsung S3 - there are various "qualities" of charging pads, this happens to be a very good one that is slightly flexible. The bad ones crack and break very easily. I trimmed it down as much as possible.
The Moto X is working great, the only thing I haven't tried is the NFC, if it does still work I would expect the range to be even shorter then normal.(I never used it anyway)
I have updated some pictures in case anyone else wants to attempt the mod, all of them taken rather quickly from my second Moto X during the mod process.
The most important is the first picture which is the USB positive connection point.
You can also see the routing I used to get a 30 gauge wire to the back side of the main board.
I trimmed the blue silicone pad to make room for the charging pad.
Sorry the pics aren't as easy to follow as they were originally, I had to upload them here instead of hosting them myself.
And something extra I want to add. The Moto X is very picky about what it will charge from. At times it will charge at full speed, other times it is very very slow. The rhyme and reason are not something I have been able to determine yet.
edit - added a better picture showing the positive connection point.