To a bowl or stand mixer, add the warm water, sugar, and yeast. Let the yeast proof for 5-15 minutes in a warm place until it is bubbling.
Preheat oven to 450˚F (230˚C).
Add in the flour and salt. Mix in the bowl until well combined and the dough comes together into a ball.
Dump the dough onto a floured surface and knead briefly to smooth out the dough and develop gluten. Form the dough into a ball and place into a new, large greased bowl. Cover with a towel and let rise for one hour or until doubled in size.
Remove the dough from the bowl, and cut 2-three ounce (85g) portions of the dough. Roll each portion out to a size slightly larger than a 9x13-inch (23x33 cm) baking sheet.
Place the first rolled dough rectangle onto the greased baking sheet. Sprinkle a thick layer of mozzarella cheese onto the dough, then place the second sheet of dough on top to cover the cheese.
Place string cheese into the edges of the dough, and fold the edges over the cheese, crimping the edges.
Brush the dough with olive oil, salt, and pepper to taste.
Bake for 20 minutes or until the crust is golden brown and the cheese is melted inside.
Quickly top the stuffed bottom crust with sauce and any extra toppings or cheese you would like.
Bake until the toppings are heated through, and the cheese has started to brown 10-15 minutes.
Transfer the pizza to a cutting board, slice, and serve.