The light ring is printed almost transparently. For me it worked fine to just print the whole thing upside down and add some support structure which was removed afterwards. The ring sits tightly on top of the main body.
I got me an LED strip composed of 60 LEDs per meter. It’s important to buy water resistant strips because those are wrapped in a transparent rubber tube that can be super glued to the 3D printed part. Just cut the thing in pieces and solder it back together to get it symmetrical. The light octagon now contains 28 independently addressable LEDs (six on both long sides, four on the two shorter sides and two in each of the four corners).
The thickness of the plastic and the infill scatter the light in such a way that the LEDs blend into each other. In the real world it looks much smoother than the images could show. The distance between the LEDs is just perfect so that one does not even see where they are located.