In this article Steve McKenzie takes us through his steps of building an LED ring light.
I used 3/4 plywood as the base for the build (I got mine in the bargain bin at the home improvement store, since any cosmetic flaws it may have had would be covered up by the duct tape.).
I used three separate LED strip lights, but I had to wire them in parallel, since when they were wired in series, the LEDs at the end were dimmer. So, I had to solder that part and reconnected it to the power cord.
I also ordered a remote control, which allowed me to dim the ring light from 100%, to 50%, and 25%.