I learned the CAD part from this guy, it was an excellent start to make sense of the UI, and then once we master the basics/design principles, the rest is easy to learn as you go. The CAD part I learned by doing and with the help of folks here on the forum.
I have never been a woodworker so I tend to think in terms of “I have a CNC, it’s the answer, whatever the question is” (which is a bad approach obviously, but I just love CNCing stuff). So I would do that as a two-sided job
- start from a square stock
- mill the top
- mill a jig that is a negative of the top
- flip the part and attach it onto that jig
- mill the underside/recess.