Bill Tindall, E.Tn.
This was a different piece of furniture to build. Normally I make a piece of furniture and fit the top to the result. My case target width of say 24" might wind up some different.
In this case the rock determined the length and thickness. Daughter specified an over hang and width of flanking walnut. I had to be especially careful with the dimensions of all the frame and drawer parts to achieve a frame that meet the size requirements. A lot of time was spent double and triple checking the size of components.