I made a small LED panel

For the diffuser, there's a nice one or two in all LED/OLED monitors. More stuff in there too, acrylic/polycarbonate glass and a Fresnel lens. Worth scavenging if you come across a broken one.

Oh that's a great idea! This also reminds me of the video where the guy took out the LED panel and used just the light and the Fresnel lens to make a window with very natural-looking light.

I think you mean "LCD/LED" monitors (where "LED" is commonly used to mean an LCD panel with an LED backlight, and "LCD" is used to differentiate old CCFL-backlit LCD panels).

OLED screens do not have a backlight and thus don't have a diffuser.

Whoops, guilty as charged. Thanks.