We'll use machine screws to secure the Feather and capactive touch sensor to the 3D printed enclosure. They can be 4-40 3/8 or M3 sized machine screws.
Mount Cap Sensor
Let's mount the capacitive touch sensor to the enclosure. First, I suggest tapping the holes on the enclosure using the machine screws. That way we can create threads in the standoffs. This will make it easier to fasten the screws through the enclosure and PCBs.
Fasten two screws into the enclosure about half way, until the tip pokes through the standoffs. Then, grab the cap sensor PCB and lay it over the standoffs so the screws are lined up with the mounting holes. Hold the PCB in place while fastening the two screws until their flush with the surface of the enclosure.
Now we can mount the Feather board to the enclosure. We're basically going to repeat that process for the Feather. The microUSB port from the Feather should be pointing towards the cutout on the enclosure.
Next up, let's mount the switch to the enclosure. No screws necessary. There's a little spot dedicated for the slide switch. Insert the switch in between the walls at an angle and press in to snap into place. The body of the switch should have a friction fit in between the walls. There's also a third "wall" that keeps the body of the switch in place. The actuator from the switch will protrude from the cutout.
Install NeoPixel to Cover
The NeoPixel ring will be mounted to the cover of the enclosure. Two circular rings will hold the PCB. Place the NeoPixel ring into the circular holder and press it in. The PCB will have a semi-snug fit. We can secure it in place using a number of methods. Glue or tape is probably fine but I ended up using mounting tack.
Install Touch Pads to Cover
OK, now we can work on installing the touch pads into the cover. To do this, start by inserting one pad through the cutout on the cover from the bottom. Then, orient the pad so the lip (or the side with the flush surface) rests on top of the cover. This way, when you press down on the pad, it doesn't pop out of the cover. It may or may not have a tight fit. Some of the tolerances differ due to the nature of 3D printing. Repeat this process for all six pads.
It's a good idea to match the pad with the pin numbers on the capacitive touch sensor. Pad 1 should be with Pin #0, pad 2 with pin #1, and so on and so fourth. The goal here is to order the pads so they're chronological with the pin numbers on the capacitive touch sensor.
If we can't determin which pad is connected to which wire, we can use a multimeter to find out. Use the continuity mode on the multimeter. Then, stick one probe to a pin number, and the other to one of the pads – you'll hear an audible "beep" when there's an electrical connection.
Installed Touch Pads
OK, now we should have all six touch pads installed into the cover. Now is a good time to double check the order of the pads. Make sure they're consistent, chronological, all that jazz.
Secure Pads and NeoPixel
Now that we have our NeoPixel ring and six touch pads installed into the cover, it's a good idea to secure them in place. Again, theres more than one way to skin a... never mind! So you could do this with hot glue, E6000 or tape. Whatever you have on hand. I personally used mounting tack. I like it because I can always remove it later without leaving behind a mess. But the goal here is to keep the components from coming out of their spots. Since 3D printing tends to have variable tolerances, the parts might pop out of place unless there's something holding it in place.
Let's go ahead and place the battery into the enclosure. It can rest on top of the components. You might think this might damage the components or wiring but, honestly I haven't experienced any issues. As long as you don't shake the enclosure ferociously, I think it'll be OK. There's also plent of room in the enclosure for some sort of cushioning, like papper or cotton? If you're worried about puncturing the lipo battery, you can wrap it in gaffers tape for extra protection. Or maybe use a AAA battery pack? Not sure that would fit. Options!
OK now for the last step. Let's fit the cover over the enclosure. The indentations on the lip of the cover snap fit into the nubs on the inside edge of the enclosure. You'll need to apply some press to get them to snap together. Fitting the cover at an angle might be helpful. Once you get all six edges shut, you should have a really tight fitting. That cover is never coming out now! JK, you should be able to pry it open with your finger nails or spatula if you ever need to open it back up.