In a large bowl, mix together the salt and water. Add the flour and yeast. Knead to form a soft and elastic dough. If the dough is too dry, add a little water. If the dough is too wet, add a little flour.
Cover with a wet tea towel and allow to prove in a warm area for 1-2 hours.
Meanwhile preheat the oven to 180 degrees C / Gas 4 with a pizza stone set on the lowest shelf rack, for at least 1 hour.
Transfer the dough onto a floured pizza paddle and gently press until the dough is 30cm in diameter or 3-5mm thick. Spread evenly with pizza sauce, tomato, sliced prosciutto, mushrooms, Italian seasoning and mozzarella.
Increase the oven temperature to 250 degrees C / Gas 10 and transfer the pizza onto the pizza stone. Bake for 15-25 minutes or until the base of the pizza is browned and the cheese is bubbly.