Already during the Minoan time olive oil was made in Crete. The olives were broken by using stones, the olive pulp was mixed with water, put in a press and the mixture that came out of the press was put in basins. As water is heavier than olive oil, the water went down in the bassin so the olive oil was separated from it and easy to recuperate.
The pictures below show you a later used way of the process.
Today machines are used.