Pendant casting newbie

[Sage37]

Hi all -
Hoping someone can help. I’m relatively new to the whole jewellery thing, but have taken a couple of courses and keen to develop my skills further. I would like to make a ‘blob’ pendant, and have invested in a lot of tools and materials to do so.

Having looked around I’m still unsure of what the best way of casting this sort of piece would be. If it achievable by casting into a charcoal block mould, or am I better off doing it in a clay mould, or cuttlefish?

Photos attached for reference of what I want to achieve. Any advice is really helpful!
Thanks in advance.