Put the 100g sugar in a small saucepan, put the fire on medium heat and let the sugar melt into a dark brown caramel, stirring every now and then. When the caramel is ready, pour into a rectangular cake tin, sprinkle the flaky sea salt (to taste) evenly over the caramel, and leave to cool in the refrigerator.
Beat the egg in a bowl. In a separate bowl, mix the coconut milk, grated coconut flakes and the 15g sugar together until the sugar dissolves. Add the egg to the coconut milk mixture and stir until smooth.
Pour the coconut mixture in the cake tin, on top of the caramel with sea salt. Cover the cake tin with aluminium foil and put the cake tin in a big open oven dish. Fill the oven dish with water, so that the outside of the cake tin is a bit more than halfway under water.
Put the oven dish with cake tin in a preheated fan oven on 180 degrees C. Let the flan ‘bake’ for 40 to 50 minutes, until the flan looks sturdy and set. If the flan fails to set, remove the aluminium foil and ‘bake’ uncovered for some minutes.
Put the cake tin with the flan in the freezer for 2 hours. After that, get the flan out of the cake tin by putting it upside down on a rectangular plate and gently patting on the bottom of the cake tin.