The choice of replacing the small marble table entirely or trying to "work around" it with walnut. The lower walnut tabletop is about 44cm by 55cm and is just low enough to give easy access to slide laptop(s) under the main table top. The top floating shelf is wide enough to happily accommodate two ipad sized tablets. The top shelf and lower tabletop are attached to the backing by steel brackets which cut through to the back through four CNC created mortises.
Cutting the mortises was interesting, I had to drop back to using a 1/2 inch cutting bit in order to service the 45mm depth of the timber. The back panel was held down with machining clamps but toggles would have done the trick, it was just what was on hand at the time. I cut the mortises through from the back using an upcut bit and the front turned out very clean without any blow out. You could probably cut yourself on the finish it was so clean.
The upcut doesn't make a difference in this job but it is always good to plan and see the outcomes for the next time when the cut will be exposed. The fine grain of walnut is great to work with CNC, though most of my bits are upcut for metal work.
I will likely move on to adding a head rest to the eames chair next. But that is a story for another day.