First we'll build a super low-profile USB extension cable so we can put our charging / programming port on the side of the handle. This way we can just plug it in to charge the battery without having to take anything apart.
This is the trickiest part of the whole project since it requires some tight soldering work. Once you get through this part, the rest is cake.
We'll need a 5-strand ribbon cable. I'm using a multicolored one for clarity. Cut the ribbon cable to 4 inches long.
Make sure you've got all the pieces. You'll need a female connector and snap-fit plastic sheath, 4" of ribbon cable, and your male connector and 2-piece plastic sheath.
Separate the wires at both ends of your ribbon cable and tin all five wires. Trim just a smidgen off the tips of the wires so they're nice and tidy.
Plug the male side into the female side for a moment, so you're 100% sure you've got both sides the same way up.
Once you're sure it's aligned right, tin the pads on the male connector on both sides. Solder the wires as shown - the first, third, and fifth wire go on the the 3-pad side, and the second and fourth go on the 2-pad side.
Plug your Feather into your computer's USB port via your newly soldered cable. Press the reset button and be sure your Feather shows up as a drive on your computer, in order to be sure the data lines and power lines are all in working order.
Once you're sure your soldering is 100% solid, clip the housing onto the male end of your cable.
Squeeze a bead of hot glue across the exposed contacts on the female end to keep them nice and secure as well.