As shown above, the capacitor and regulator can be mounted and wired on an Adafruit Feather Proto-Wing. 12v and the NeoPixel strip are also connected to the wing.
Above you can see the USB and Power jack attached to the case. The USB breakout fits snug enough that you may not need anything further. If not, a couple drops of super glue will fix it in place. A 2-wire JST connector was used to make installation easier. The power wires are a little thinner than might be ideal, but it works. The matching connector/wires are used to connect power to the wing.
The feather is attached to the printed mounting plate with the M2.5 screws. Metal ones are listed, but if you have a set of nylon ones, they'll work as well but might take a bit more effort to get threaded. Attach the tray to the frame (as shown in the image below) with some superglue.
First, use superglue to attach the Feather mounting plate to the frame near the power and USB connectors. Once that has set, carefully glue the four frame pieces together.
It works well if you glue pairs of pieces together, being careful to get everything lined up exactly. Then take the two frame halves and glue them together. You'll notice that one of the pieces shown is different. It was a previous iteration of the design but was functionally the same. No point wasting it.
The strip can be attached to the lattice of the frame with drops of superglue. Coil it loosely so as to get the light spread throughout the space. It's a good idea to connect it to the controller first to ensure that the wired end is close enough to be connected.
This is a good time to load the code onto the Feather if you haven't yet. This will also ensure that the USB jack is securely mounted and won't get pushed out of place if you later try to plug into it.
Use the corner and side mounting pieces to attach the acrylic plate. This can be a little fiddly.
Start by fitting the corner pieces onto the plate. The slot the plate fits into will be filled with support material and has to be well cleaned out. Test the fit as you go and clean out what you need to in order to have the plate fit smoothly all the way in. It needs to go all the way into the corner.
The side pieces print without support so they shouldn't present any problem.
With all mounting pieces on the plate, gradually work the pieces into place on the frame with the side pieces centered over the joint between the pieces of frame. This serves to strengthen the frame. You will likely need to carefully tap the corner pieces onto the frame a little at a time, going from corner to corner.