A while ago, electronics tinkerer and programmer extraordinaire CNLohr released an informative video on how to make glass PCBs.
The video inspired Instructables user mosiver to attempt (and succeed at!) using the technique to make a 4×4×4 RGB LED Cube. Using microscope slides made out of glass together with copper tape, which is conductive, mosiver manually built circuit boards to carry surface mount RGB LEDs. The glass slide PCBs were mounted onto a prototyping board that kept them upright, as well as connected the LED arrays to an Arduino Nano microcontroller.