Important caveat: This guide covers only the construction of the stand and diffuser, not programming the LED. That sort of thing is covered at Adafruit's site.
3mm clear acrylic
3mm opaque white acrylic
26 gauge stranded wire
22 gauge solid wire
Epilog Laser Cutter
CNC Vinyl Cutter (Optional)
Corel Draw 5
Step 1: Laser Setup
If your laser's kerf is also 0.25mm you can use the attached files directly. If not you'll need to redo the diffuser box design. The diffuser is simply a 40X40X40mm (exterior) cube with custom cutouts in the center of the top and bottom plate. If you need to regenerate the diffuser start with a design from the excellent utility at rahulbotics then copy in and center the cutouts.
Step 2: Create the Hardware
Cut the indicator stand out of clear acrylic. Then cut the the diffuser out of white acrylic.
If your kerf measurement was correct the indicator cube should go together with minimal pressure and stay together without adhesives. Make sure you align the top and bottom cutouts and remove any masking material before pressing the cube firmly together (a well done cut will be difficult to pry apart later).
Lastly the indicator stands needs to be bent 90 degrees at the base. You can use a plastic bender for this.
Step 3: Create Masks
One of the best looking but time intensive methods is to use a CNC vinyl machine to cut black adhesive vinyl. You'll probably need adhesive delaying solution like rapidtac to get the positioning perfect.
The second best (but much faster) method is to print onto transparency paper then glue the mask to the front of the cube.
Regardless of the technique you choose you want artwork that is about 34 mm square.
The icons I used for this build are from the UN and are available here.
Step 4: Solder
Solder three 18 inch lengths of 26 gauge stranded wire to the inputs of the Neopixel board. Because these are stranded it's important to tin the tip of the wire before attaching it.
Step 5: Assemble
Clean the bottom of the stand with rubbing alcohol, then cut velcro to size and affix it to the underside of the stand. Attach a second layer of velcro to the first then press the assembly down on top of your TV or monitor.
Finally attach the diffuser cube to the stand. It should slide down smoothly and rest securely against the stand making contact on the top and bottom sides of the cube.