All materials have low thermal conductivity. Rubber keeps water out.

Wood blocks for texture and volume(wall-thickness).

Silicone rubber for water-proof quality.

Rubber heavier than wood. When rubber is poured into the tray, wood blocks naturally float up wrapped in a layer of rubber.

Plaster for adding rigidity. Metal mesh half cast in plaster and half in rubber for locking up different materials.

Product façade. It should be thicker if more material allowed.