Replying to
@jess@blop.social
Most of the neon flex LED stuff is about 25 mm deep. If you can get the backplate routed and then feed it in, you should be good no matter what you make the plate out of.
e.g. https://www.weloveleds.co.uk/collections/led-flex
There are some smaller ones but they will need soldering rather than having push connectors (that site has some)
Sharp angles are going to be your problem though