Help with SketchUCam

I am fairly conversant with Sketchup, but new to sketchucam.
I am trying to make a box, that bit I have worked out, but what I can’t get is how to create a lip on the inside of the top, for a lid to sit in, can anyone help me here. thank you.

Can you upload your SketchUp file so we can see what you have so far?

Ok, thaks for the reply.
Box3 is what I am looking for, but this will not work in a CNC.
Box2 is what I am trying with SketUCam everything is fine except I cannot get the recess for the lid to sit in.

Box3.skp (1.2 MB)
Box2.skp (1.3 MB)

Have you tried getting assistance from their forum?