After two years of learning, thinking, and tinkering, I finally finished my first intarsia cabochon. Unlike the usual composites of straight-edged pieces, this includes a concave freeform center piece.
The whole excercise turned out quite complex, and describing all the steps, considerations, dos and don'ts, and options would easily fill a book. Roughly, the process involves choosing slabs of similar thicknesses, cutting preforms (your choice of sawing, flex shaft, drilling, etc. depending on the design), sanding sidewalls with slight angle for conical fit, and vibratory or ultrasonic grinding using an abrasive slurry to get pieces to grind each other into a perfect fit. Then there is the epoxy, cleanup, and finally cabbing or flat lapping. Easy-peasy.
Now that I've convinced myself that I could do this, it's time to actually consider the aesthetics of the materials and the form and composition. I think the next creation might have two or more inlaid pieces, with more contrast than what you see here.
I also want to thank all of those in this community who share their insights and knowledge. As a beginner, I learned a lot in this forum.