In a large mixing bowl, combine the starter, flour, and sugar. Slowly add 3/4 cup of water and stir. If the dough does not come together, add more water a bit at a time, up to 1 cup total. The dough should be sticky and shaggy but not wet. Cover with damp towel and allow to rest at room temperature for 30 minutes to an hour.
Add the salt and knead by hand to incorporate. One minute of kneading should do. Stretch the dough out to make sure the salt is incorporated then reshape into a ball and place in a greased bowl. Cover with damp towel and let rise at warm room temperature for 2 hours. An oven warmed slightly and then turned off works well.
Prepare your baking sheet either with parchment or non stick spray topped with a generous amount of cornmeal.
Gently shape the dough into a ball by pulling up from the bottom and pulling towards the center. Flip it onto the prepared baking sheet.
Cover with heavily greased plastic wrap and allow to rise at cool room temperature for 1 hour.
After 1 hour, preheat your oven to 450 degrees with an empty baking sheet on a lower rack. This will be needed to create steam in the oven. Remove the plastic wrap from your rising loaf and rub flour into the top without smashing it. Slash deeply using a serrated knife. One slash down the center will be fine. Recover and allow to rise one more hour as oven finishes preheating.
When oven is hot and bread looks puffy, pour 1 cup water into hot baking sheet in oven to create steam. The sheet may buckle, this is okay. Immediately place loaf inside and bake for 30-45 minutes until well browned.
Allow to cool completely before slicing, at least 2 hours.