Need Help Best way to backlight evenly?

Hello everybody, hoping you can give me some advice.

I'm trying to make a backlit sign out of a small wooden box (30x20cm). I was planning to cut out whatever the design is on the front and then put a piece of opal acrylic behind it to act as a diffuser. I was going to light it with LEDs and run them around the sides of the box.

What I'm looking for is a simple way to spread the light more evenly across the sign. So far I've tried to create my own light sheet by engraving dots and a grid on some acrylic and then edge lighting it. This didn't seem to make a huge difference but maybe I did it wrong. Then I tried putting a piece of kitchen foil on a back panel, this seemed to work quite well. I was just wondering if there was a more professional way of doing this.

What do you guys think?