Step 1) Leonardo Sketch App
This is my quick sketch I did last night in Leonardo (link). Its a multi-medium pen multi-layer sketch app for tablets and is easy to use.
Step 2a) Meshy AI to 3D (link) SketchFab model (link)
I Used Meshy 3D to create an instant AI generated 3d model. I remember seeing them at GDC but at the time their model wasnt fully flushed out. Trying it again now I see they are getting really great results even out of this very simple first test from a rough sketch. I suspect their training data and methodology has grown and evolved since those early days...
Step 2b) META SAM 3D Segment Anything (link)
I Used Meta SAM 3D to create an instant AI generated 3d model
Step 4) Detail modeling in 3D apps 3ds MAX, Blender, Substance ...
High detail modeling in Autodesk 3ds MAX or Blender