The diodes are directional. Extra flux will be helpful.
Bottom of the Left Hand Side
Jumpers
Bridge the jumpers for the microcontroller breakout board. Make sure the correct side is used.
Top of the Left Hand Side
The Microcontroller, TRRS Jack and Reset button
Solder the microcontroller with the pin headers or sockets. Make sure it's the correct side and align the pins correctly. For Sea-Picro, do not solder the D+ and D- pin.
Top of the Left Hand Side
Test the Key Presses
When you connect the left side to the computer, short the hotswap socket pads to trigger key presses with a wire or a pair of tweezers.
Solder the Right Side
Repeat the above steps for the right hand side. Test the keyboard by connecting the TRRS cable, and the left hand side to the computer. As a reminder, do not plug/unplug the TRRS cable when the keyboard is powered.
Hotswap Sockets
After testing both sides, solder the hotswap sockets.
Bottom of the Left Hand Side
Final Photos
Although Sea Picro provides 3.3V, the RGB LEDs might still work. It's not guaranteed that the RGB LEDs will always work with 3.3V. It's recommended to power the RGB LEDs with 3.7V-5V with Sea Micro.