Here are major steps to build a DiscoBall from the triangle modules.

All the triangles comes with mouse bites in a panel. Trim the edge and make it smooth and even.

These WS2812B-2020 LEDs are not that difficult to solder. The four pads are big enough for manual soldering.

Tape a pair of triangles. The top side with LEDs is facing down. Three through-hole resistors are used here. Match the side with O (output) with the side of I (input). Square to square.

These through-hole soldering is easy.

Here you have to estimate of the cut. 

Get the right triangle out and these wires into three via-holes of the right triangle, which is vertical. Now move the right triangle into the horizontal position and align it with the left triangle.