Member Spikenzie etched his own 88 LED matrix PCB. He’s also posted helpful instructions and artwork used in his process –

The 88 LED matrix is a building block. There is no processor or circuitry other then then LEDs and the copper traces. It is simply an eight by eight 64-LED matrix on a PCB. The 88 has 16 pins on one edge, 8 connect to the rows and the other 8 to the columns. This allows the maker to use their preference of controlling circuitry.

The way a matrix works can be a bit mysterious at first. Of course building one yourself is the best way to learn

DIY 8×8 LED matrix