Preheat the oven at 150 degrees Celsius.
Place a baking papers on 2 baking sheets.
Mix the seeds, flour and olive oil in a bowl.
Pour the water in a casserole and let it boil. Pour it in the bowl with the seeds and mix well.
Divide the batter in 2 and flatten it out over the baking papers so it becomes very thin.
Place in the middle of the oven 1 baking sheet at the time for 1 hour. Take out the first crispbread and sprinkle half of the flake salt evenly on the bread. Repeat this step with the second bread.
Let the crispbreads cool down and break in big pieces before serving it.