I think you'd be far better off to make a custom PCB in whatever shape you like from the like of JLCPCB, PCBWay, or others. The WS2812s here all connect to eac

I think you'd be far better off to make a custom PCB in whatever shape you like from the like of JLCPCB, PCBWay, or others. The WS2812s here all connect to each other in series, so if you cut the board down, you'll have to replace the cut connections with bodge wires. To my mind, that plus the cutting is way more work than just making a PCB in exactly the shape you want. You can get cheap PCBs for $5-$6 for qty 5 100mm x 100mm boards delivered to your door in the US. Add on LEDs at $0.03 to $0.05 each and I'd way rather make than modify here.