Dissolve salt and sugar in 1 1/2 cups warm water that is between 100° and 120° F. (Warm water is needed to activate the yeast, but if it is too hot, it will kill the yeast. Use a candy thermometer to test the temperature.) Stir in entire contents of packet of yeast and allow the mixture to "form a head" (like on a beer), which takes about 15 minutes. 

Place flour into mixing bowl and add yeast mixture. Stir to combine and then knead until the dough comes together and is a cohesive mass. Knead for a few minutes so the dough becomes elastic. Cover bowl with a clean cloth and allow to rise and rest for 30 minutes. Then punch the dough down, knead again briefly, cover the bowl with the cloth and allow to rise a second time. 

Preheat oven to 450° F.

Grease the surface of the deep-dish pan where the dough will be in contact with it, including the edges. Stretch the dough into about a 14-inch circle which is thicker around the edges. Transfer to a lightly greased 18-inch pie pan and press the dough evenly to fill the deep-dish pan, including up the edges. When the dough covers the entire surface, lightly shake cornmeal over the dough. Proceed by adding ingredients in the desired order. Bake until the edges are golden brown and the pie sets up, about 10 to 15 minutes. Serve immediately.