I took LED strips and measured the length and width of the board,
Cut Those strips to the correct length and then cut 2 more strips the same.

I soldered 90-degree connector strips to the LEDs to make a rectangle shape, 
leaving one corner unconnected so I could attach wires and a connector for the Arduino nano to plug into.

I placed Kapton tape on the backs of the LED strips so they wouldn't touch the metal surface of the sand board and short.