So you have already bought an Apple Watch but want to build your own charger for it? The folks at Adafruit have put up a video that shows how you can build a wireless charger for Qi compatible devices like the Apple Watch. You will need an Adafruit Powerboost 1000C, a 2000 mAh battery, and a slide switch to build your own wireless charger.
A 3D printed enclosure is also required. The good news is All the parts and information about this wireless charger are included on adafruit.com.