Put the sourdough in a large bowl along with water (or water and milk) and mix well with a spoon until it is dissolved completely.
Add the flour and mix using the spoon, when the mixture is almost omogeneous add the oil and salt and go on kneading until you get a soft and smooth dough. Cover the bowl with a clean cloth and let it rest at room temperature for a couple of hours. **
Brush lightly with oil a 13x12 baking pan and spread the pizza dough into it using a spoon to distribute evenly. Season by spreading some tomato sauce then let the pizza rise for one hour.
Bake the pizza in a preheated oven at 400°F for 15 minutes, add any other ingredients such as mozzarella cheese, grilled vegetables, etc... , add a pinch of salt and plenty of oregano then bake 5 minutes more. You can now enjoy your homemade soft, whole wheat sourdough pizza!