Sift flour into a large mixing bowl. Add yeast, sugar and salt. Make a well in the centre of the flour mixture. Pour in oil and water. Mix to form a dough, adding more water if needed. Knead for a few minute until smooth and elastic. Place in a lightly oiled bowl. Cover with oiled plastic wrap and leave to rise until doubled in size. Punch down dough, add rosemary and place in a well-buttered pot (with lid). Place pot in cooled-down coals. Ladle coals over the lid (to ensure a crisp crust) and leave to cook for about 1 ½ hours. Test dough with a metal skewer or tap the bread – the loaf should sound hollow. You can also bake this bread in a preheated 180°C oven for 50–60 minutes or until cooked through.