Here’s an update with just some work-in-progress images while I was putting together the hardware.
Soldering the components for the diamond: the first try kind of failed because it was so messy while I tried to get all connections to fit on the tiny board. I also forgot to include the capacitor for the motor. The second try was much neater and I got everything right because I had the first one for visual reference.
On another note, I found a quick way to remove the copper strip from the board with just solder and pliers: