We have to deduce a physical process by which a solid ball of stratified sediment, the Earth at the end of the second day, is formed into a hollow sphere with a hydrological system by the end of the third day.
The Potter’s Hand
Formed: יֹצֵ֨ר – yatsar
Part of the meaning of the word translated as "formed" is pictured by how the potter's hand shapes a hollow vessel from a solid lump of clay.