Proof the yeast with sugar and warm water.  It should look like a latte after 15 minutes or so.
Add 5 cups of '00' flour and a pinch of salt.
Blend until its slightly sticky.  Add water if needed.
Turn out onto a floured surface and hand knead until you feel it soft and elastic, about 10 minutes. Let it rise on counter for a few hours, cover then put into refrigerator overnight. 
Remove from refrigerator and from the bowl, then place into a larger container and leave on counter to rise again for a few hours. 
Remove from the container and place in large, oiled Pyrex / baking pan. Spread dough evenly in pan, sprinkle olive oil and Sea Salt on top and then plunge your fingers into dough, making small wells.  
Once this is done, you can decorate with your favorite toppings. 
We like to place thinly sliced mushrooms on some and an Italian herb mix across others.

Bake at 390 degrees for about 20-30 minutes.  Once the top turns golden brown, remove from oven.

Slice into squares and serve warm or cold. Be sure to have a small bowl of EVOO to dip your Focaccia into and of course, a glass of Sangiovese! 
Mangiamo!