• In a large bowl, dissolve the yeast in the warm water (see Notes). Using a rubber spatula, stir in 525g flour and the salt to form a soft, sticky dough. Do not knead. Cover with lightly greased cling film and let it rise at room temperature for 1 hour.
• Stir down the dough (it will be sticky). Turn it onto a floured surface and with floured hands pat it into a 22cm square. Fold the square into thirds, forming a 22cm x 7cm rectangle. Fold the rectangle into thirds, forming a 7cm square. Place it in a large greased bowl, turning once to grease the top. Cover again and let it rise at room temperature until almost doubled, about 1 hour.
• Punch down the dough and repeat the folding process. Return the dough to the bowl; refrigerate, covered, overnight.
• Grease the bottom of a disposable foil roasting pan (see Notes) with sides at least 8cm; dust the pan with the polenta. Turn the dough onto a floured surface. Knead gently 6 to 8 times, then shape into a 15cm round or 20 to 25cm rectangle loaf. Place it into the prepared pan and dust the top with the remaining 1 tbsp of flour. Cover the pan with lightly greased cling film and let it rise at room temperature until the dough expands, about 1 hour 15 minutes.

Shape and bake the bread:

• Preheat the oven to 260C. Using a sharp knife, make 1 slash across top of the loaf if you make it a round one, or 3 slashes if you make it a rectangle shape. Cover the pan tightly with tin foil. Bake the loaf on the lowest oven shelf for 25 minutes.
• Reduce the oven setting to 230C. Remove the foil and bake the bread until it is a deep golden brown, 25 to 30 minutes. Remove the loaf to a wire rack to cool.