Measure the flour into a bowl and cut the butter into the flour using a pastry cutter. Add as much buttermilk as needed to form a sticky dough. Turn out onto a floured surface, sprinkle with additional flour, and fold the dough onto itself a few times. Using a pizza cutter, cut the dough into biscuit-sized portions and shape with your hands into rounds. Put the butter into the bottom of a cast iron skillet and place it in the oven for a minute or so to melt. Arrange the biscuits in the skillet and bake until browned and puffed, about 12-16 minutes.