I used Anycubic water washable clear resin. I tried various substances to fill in the area and ended up using a black polymer clay that requires baking at 250F to harden. It seems that heating it up or cooling down too quickly may cause the resin to crack (though not totally certain, just anecdotal).

I used 0603 red LEDs, eleven in series with an inductor/capacitor, to provide the lighting. I used a wireless LED lighting kit bought off amazon and desoldered the inductor/capacitor to use.