References: Mold Making, Tetris Ice Cubes, Vacuum Chamber
Design, carve the inverse into something that would make a good silicone mold, make the mold and freeze. You want a vacuum chamber for the mold so there isn’t air bubbles, I have a few vacuum pumps but I question how low they can get the air pressure.
What to mold:
Fruits
Bunny, animals
Penguin on iceberg
Tooth mould
Titanic
Brain
Paw print
Musical instruments
Chess set
Fossil
Halloween: ghost, skull
An open source superhero logo
A person frozen in a slab of ice