In a small bowl, dissolve dry yeast and sugar in 1/2 cup of lukewarm water. Let sit for 10 minutes until it bubbles.
Meanwhile, stir 3 1/2 cups flour and salt in a large bowl. Make a well in the center and pour in the yeast mixture. Stir with a wooden spoon until a raggedy dough shapes. Pour in another cup of lukewarm water and stir. It will be very liquidy. Add the remaining flour, if needed, and stir until a dough begins to take shape.
Place the mixture on a lightly floured clean surface and knead for about 10 minutes until a smooth, elastic dough is shaped.
Place in a large bowl greased with olive oil, cover with plastic wrap and set aside to rise for 2 hours. After the dough has risen, punch it down and divide in half. Roll each half into a long rope and seal the ends together to form a circular or oval shape. Place on a parchment paper covered baking sheet and let rise another 30 minutes.
Meanwhile, preheat oven to 350F. After the second rise, bake the bread until golden and it sounds hollow when tapped underneath, about 30 minutes.
Remove from the oven and let sit until cool enough to handle. However, do not let it cool completely or it will be more difficult to cut in half.
With a sharp knife, make a slit on one side of the bread and use string (I used butcher's string) to slice the bread in half. You can definitely use a knife to do so, however the string leaves the surface of the bread with indentations which catch the olive oil or other seasoning you may use to serve it with.
Reduce the oven temperature to 225F and bake for approximately 2 hours or until the bread is completely dry and cracks easily. Let cool and store in a paper bag in a cool dry place.