Snap off all external boards. Don't split the sidebars if you're using 5x6.
Use a knife/file to scrape off the jagged edges of the PCB joints.
The 4 triangle pieces can be soldered onto the 3 pads near the USB ports to reinforce that area.
Use the supplied pin headers to line up and solder the spacers onto the top of the LED board.
Place the spacer down on a hard surface, then the PCB on top.
Put the pin header through the holes, and push the plastic housing down.
Flip the boards over, and make sure the holes are lined up.
Solder the pins in, make sure no solder or pins are above the spacers.
Trim the headers off on the bottom.
Solder switches on with plate/case.
Trim the pegs and pins as low as possible (<2mm height).
You may want to do this in the PCB or out, whichever is easier for you.
Be careful not to break any of the surface components on the PCB.
To configure USB ports: There is a column of 3-pad jumpers above the MCU. Solder the middle pad to the pad in the direction of the port you want to connect to the PC. Do this for all 4.
On the slave side, solder them in the opposite direction.
You will also need to solder SJ2 on the master side. To flash the slave, put some tweezers in the adjacent holes to hold the connection.
Place nuts into cutouts. You may need to push the switchplate back down and/or force the nuts in.