Preheat the oven to 200C. Line a baking tray with grease proof/ non-stick paper.
Rub the the butter cubes, flour and salt together until the mixture resembles breadcrumbs. To get the large pieces of butter up to the surface, shake the bowl.
Gradually add the water until the mixture resembles a soft dough. If it is too stiff after the 200ml add a little more.
Knead for a minute or two (just gently) until all the dough is fully combined and the salt is evenly dispersed.
Turn out onto a floured surface and shape into a large, thick disk, roughly 16-18cm wide, but it varies. Make 8 deep slashes across the top in a compass shape. Bake for 30 minutes. After it has turned crusty, turn the oven off and leave until ready to eat.