Let us think to a small PCBs and one solder the edges. Metallized edges are not standard and 6 PCB is not cheap. How to test before assembly? How to hold pieces during assembly?
We solved these problems with a simple PCB design using V-grove scoring (like chocolate) and plated through holes just in the middle of scoring. So the contact is established before breaking the circuit, and when positioned at 90 degrees, the half metalized holes are ready for a drop of solder.
A tricky path on the PCB allows to test the LEDs and develop the initial software for the WS2812B LEDs. Neopixel and more compact libs like the WS28 lib can be used.
The RGB MiniCube is available now on Tindie.