Mount the cube. That sounds very easy, but it's not. You have to align 64 LED legs to slide through 64 holes at the same time. It's like threading a needle, times 64.
We found it easiest to start with one end, then gradually popping the legs into place. Use a pen or something to poke at the LED legs that miss their holes.
Once all 64 LED legs are poking through the base, carefully turn it on it's side. Then bend all 64 legs 90 degrees. This is enough to hold the cube firmly mounted to the base. No need for glue or anything else.