Mold and Cast of BJD Knee Joint Ball Part with Magic Sculpt

What am I trying to do here? I need to make a mold for this part (double balls for knee joints) - see the photo just below. I need a part, consisting of 2 balls, which are  connected, flattened on each side, with the vertical central hole. Why can't I just roll some clay in…

Ball Jointed Doll Mold - Sweden

Molding and Casting A Ball Jointed Doll

Volks Super Dollfie Cute discussion Part 2, Page 2

I want to make my own BJD

bjd — News — STAND

How to Make a Ball Jointed Doll (with Pictures) - wikiHow

Casting Hooves in Resin - BJD- Ball-Jointed Unicorn Doll - MakingFairies.com & SculptUniversity.com

Monkfish's dolly ramble: Ball joint dolls (BJD)

Ball Jointed Doll Mold