You will need an extra large rectangular (preferably non-stick) roasting pan or deep tray, 40 x 30 cm (17 x 12 in).
Combine the flour, yeast and water in a large bowl and knead with your hands or with the dough hook in an electric mixer until a very soft, almost runny dough is formed, about 5 minutes. Add the feta cheese and mix through the dough.
Pour half of the melted butter into the pan. Pour the dough into the butter, flatten with a spatula and your fingertips and top with the remaining butter, making sure the dough is covered with butter on all sides.
Cover with another roasting pan or deep tray, facing down (so that the dough has room to rise) and then cover with a towel for 2 hours or until doubled in volume.
Preheat the oven to 200C conventional (390F).
Sprinkle the grated cheese over the dough and bake for 35 minutes or until golden and crisp on top and bottom. Remove from the pan onto a board and cut into large squares to serve.
Best eaten warm. Store leftovers in the refrigerator for up to 3 days and reheat for 15 minutes at 200C to serve.
Serves 12.