Have a writing desk with a breadboard end. Sorry about the poor picture quality, but what the photo tries to show is the sides and ends as a “frame” around the central part of the table top. The frame is 30 mm (1 1/8″), while the central part is perhaps half of that. The inferior face of the frame is chamfered; all in all making the top look less thick.
This design appears to allow for grooves along all edges, that can be planed on the bench. Add a rebate on the inside of the upper face of the frame, and the centre board (having a corresponding rebate to its inferior face) could form a lap joint with the frame.
Not entirely convinced I am able top put something like together, though…
London, UK; Boston, MA