Here are the two cabinets that will have the lighting I mentioned in part 1.

I'm also making shelves that will go above a different cabinet, 
These will be 3" thick with a flush top and bottom.
I start by cutting the tongues on the fronts of the shelves.

No fancy measuring tools needed, just mark a few lines and double check with a tape.

Next cutting the groves for the tongue. Make a test piece, double check with tape.

When happy with the fit cut both edges,  top and bottom.

Measure the inside, between the grooves, and make a frame to fit in between,
Then glue and clamp the front on ,  cut to length when it's dry.

Thanks