This is a build guide based on the Helix GitHub page. The original documents are Japanese but I've done my best here to translate that guide to English.
Note: I am working on pictures, please reference the Japanese guide for further detail. Some things regarding the Japanese guide are not the same, such as how they mounted the pro micro. I will update the page as soon as I can.
Parts (per side)
Pro Micro x1
TRRS jack x1
Tactile switch x1
Acrylic plate set x1
1n4148 Diodes x32 (5 row) or x25 (4 row)
If Kailh Choc switches:
M2 spacer, 4mm x6
If Alps or Cherry style switches:
M2 spacer, 7mm x6
M2 space, 8mm x2
M2 screw, 5mm x16
Underglow LED strip x1
Per key RGB LEDs x32 (5 row) or x25 (4 row)
If you are going to use the 4 row variant, now is the time to break away the bottom piece of the PCB.
If you are going to use the OLED screens, now is the time to solder the jumpers for the OLEDs. These can be found at the bottom of the sockets for the Pro Micro. You need to jump solder between the two pads as shown below. This must be done to each PCB on the side which the OLED will mount. Do not solder the side of the PCB facing downwards. Do not solder both sides of the PCB as well.
First step in the build is soldering the diodes in place. Through hole LEDs are a bit easier to work with, so that is what you will have if you bought the kit. [CLARIFY DEPENDING ON ACRYLIC THICKNESS 3mm or 1.5mm
Next is LEDs. If you chose to do per key LEDs, there are some very important things to pay attention to. Keep your heat around or below 220 celsius. The LEDs are very heat sensitive. The PCB silkscreen, that being the white imagery, has indicators next to each LED hole. These indicators show which direction the LED should face. Here's a picture to give a better idea of what I mean.
Solder each of the 4 poles for each LED like so.
Next, do the TRRS and reset switch. Here's how the TRRS should mount and solder.
My recommendation for the reset switch is to keep the legs as is, but load the through hole with solder first. Then you can simply rest the switch on top like so, and then add more solder onto the leg. This gives a solid connection.
Solder the pins to the Pro Micro.You can use the PCB to hold the legs while you solder them to the Pro Micro. Be sure to face your Pro Micro downwards like so.
You can then solder the pins to the PCB.
Solder the pins to the OLED module, you can use the PCB to hold this as well. Be sure you do this AFTER the Pro Micro.
Solder the pins of the OLED module to the PCB.
Now you can do the RGB strip, the header is located here.
Solder the strip like so.
And finally, you can insert your switches into your plate and PCB and solder those as well.
Screw in the OLED spacers from the bottom of the PCB like so.
Screw in the acrylic bottom spacers from the top acrylic piece.
Screw in the OLED protective acrylic plate.
Screw on the bottom protective acrylic plate and stick on the feet