In 1/3 cup warm water dissolve the yeast, and let stand for 5 minutes.
Add about 2 cups of the flour, 2 tablespoons oil, 1 cup warm water, and the salt, and beat. Add more flour, mixing well, until the dough holds together in a rough mass. Lightly flour a board or work surface and knead the dough for 10 minutes, or until it is smooth and elastic.
Put in an oiled bowl to rise, covered with plastic wrap. When the dough has doubled in bulk, about 2 hours, punch it down and divide in thirds. Let rest for 5 minutes.
Preheat the oven to 450°F. Roll the dough with a rolling pin or stretch it over your fists until you have three 14-inch circles. Place on pizza pans or cookie sheets and prick all over. On each circle, spoon 1 cup tomato sauce; sprinkle with 1 cup mozzarella and 1 teaspoon oregano. Drizzle with about 2 tablespoons olive oil.
Let rest another 10 minutes and then bake for about 18 - 20 minutes, until lightly browned. To test for doneness, lift an edge-if the bottom has turned golden, it is probably done.