To simplify wiring, the boards are made to daisy chain like a cordwood module. However, to get things to line up, each column of LED boards have to rotate 90 degrees. You can see several videos about the project below.
We’ve covered EasyEDA before. It is a browser-based tool for defining PCBs and includes many other features like simulation and autorouting. You can download the CAM files from the tool or you can order the boards directly from the site very easily.
[Hari] apparently likes LED cubes large or small. EasyEDA, by the way, isn’t the only browser-based solution out there.