How to Build a Custom NeoPixel Matrix
But 1000 5mm NeoPixels from AliExpress (click here)
Using the template (click here), design your faceplate and cut it on a CNC machine. Note that you'll need to clone this repository, then navigate to the "~/readme/Custom NeoPixel Matrix" folder. From there you can open the "faceplate template.dxf" in your favorite CAD editor.
Install the NeoPixels. Through trial and error, I came up with a system that works pretty well, You can put in 10 pixels in about 20 minutes, once you get past the learning curve. These pics should help get you started:
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Short video build-90