On Thursday, May 28, 2020 at 7:00:54 AM UTC-5, DerbyDad03 wrote:

How about making a flat surface, sort of a faux top, to sit both the
slab and the wooden frame on?

The slab would be fully supported and the frame could be sized to be flush
with the slab.

Either the weight of the slab would hold the frame from sliding or dowels
(or something similar) on the underside could hold it in place.

That's essentially what I did in trying to make my frame flush with the marble top. The problem is getting the slab's edges perfectly flush or butted up perfectly against the frame's cutout edges. Unless one has specific tools for mating those edges, perfectly, there will be small gaps in the edges' fit. Without the specific tools, one would have to be very patient and careful with hand-cutting/sanding for a perfect fit. I perceive Hawk is in the same shape as I, 1) first attempt at this sort of thing (similar to first attempt at crown molding) and 2) in not having the specific tools for getting a better fit than I got.

When it comes to flush fitting frame-to-slab, the above is the issue/problem, not how or if the top's assembly is attached to the carcass.

I would suppose, if a DIYer has one of those hand-held CNC router thing-a-ma-jigs, that helps guide your cutting, then a more perfect cutting can be achieved, as opposed to using the typical cutting tools/techniques a DIYer has on hand. The flush-fit problem is more difficult to resolve with curved cutting/fitting, as opposed to cutting straight lines, for inserts as Hawk wants, as I wanted.

Leon's project solved a particular aspect of the issue, but his frame is not flush fitting with the slab's surface. It's an example of how to avoid the problem for us DIYers with limited tools.

Sonny