Place the cake pan in a large pot. Heat water in a kettle. Pour the water up the side of the cake pan to about 75% of the way. Cook on medium heat covered for an hour. Refill water every 20 mins.
Place the flan in the fridge for 4 hours to set. Remove the foil. Place a flat plate on top and flip the flan. You may need to run a knife around the edges.