Normally, keycaps with a length of 2u or greater require stabilizers which would complicate this relatively simple build. The 3u spacebar we’re using can be mounted directly on 3 individual keyswitches. This means we get to skip the stabilizers, but it also means the spacebar will be harder to press than the other keys.
If a harder-to-press spacebar bothers you, you can use a small flathead screwdriver to open the keyswitches on either end of the spacebar and remove their springs before soldering. Doing so will leave only the force of the center switch's spring required for actuation.
Mount the diodes on the PCB with each diode’s stripe pointing toward the upper edge of the board as seen in the photo above.
Once you’ve double-checked each diode’s orientation, bend their leads outward to hold them in place.
Solder each diode in place.
Clip the excess leads off the back of the board.
Save one of the clipped leads to use as a jumper in the next step.
If you're working with a single-sided PCB, you'll need to install a single jumper wire in the location shown above in blue.
Bend a clipped diode lead from the previous step into a ~5mm U shape.
Mount the jumper in the center of the top side of the PCB.
Bend the jumper leads outward, solder, and clip any excess from the board.
Use flush cutters to cut a strip of male header pins into two 5-pin length pieces.
Mount the header pins on the PCB with the longer pin ends protruding out the bottom copper side of the board.
Mount the Trinket M0 using the pins on the top side of the board as seen in the photo.
Carefully solder each pin to the Trinket M0.
Turn the board over and solder the pins to the bottom side of the board.
Clip the excess pin lengths on the bottom side of the board.
Mount a keyswitch on the PCB, ensuring that all of its pins & plastic posts are poking out the bottom side of the board.
Solder both of the switch's pins to the bottom side of the PCB.
Repeat this process for each of the remaining switches.
Once soldering is complete, go ahead and install the keycaps by pressing each one firmly onto the switch stems.
Finally, install the standoffs at each corner of the PCB using a small Phillips head screwdriver