I actually didn’t use any adhesives, I just ran (4) through bolts, in case I had to work on the LED controller.
On the top plate I used (4) of these to hold everything together, then just ran botls up from the bottom.
For the LEDs I bought a RGB LED kit and cut the strip to length.
I can attach better drawings if you are interested.
The Blues one is shown above, but I also make a Batman and Game Of Thrones plate for that base.
I made it so you can easily change the sign.