Hi Gunter,
I have modified my method so using fillet to cut the ring to form the facets is not required.
The extrusion and boolean is the same but have added some trim curves then the edges are lofted etc.
Cheers
Barry

Sorry i have not seen that was a 3DM !

So same method with the Rail Revolve (possible because same Top and Bottom profil )

Then View Points and move bottom pts horizontally to the ring

Take these new surface Top Bottom Face / Planar

You have a solid

Applyy any boolean DIff with trapezoidal profil if wanted (not made here)

Boolean Merge with The Ring (ring)

You have some draft variations for explore that you want...