Place 150g (5oz) sourdough starter in a large mixing bowl. (Remember to replenish the starter after you have made your dough, see below. ) Make up to 450g/1lb (2 cups) with water and add 500g (1lb 2oz) bread flour and salt.
Mix to form a rough ball of slightly sticky dough. The dough does not require kneading just mixing until the flour and water is combined.
Leave in the bowl and loosely cover the bowl. Leave overnight or for about 8-10 hours depending on ambient temperature. The dough will have risen and increased in size.
Knock back the dough and shape into a ball, you can knead lightly if you like but it is not essential. Place smooth side down in a well floured banneton (special basket) or in a 20cm (8in) wide mixing bowl, lined with a tea-towel and well floured.
Dust the top of the dough with a little more flour. Cover loosely and leave for a further 4 to 6 hours until risen again.
Turn out of the basket or bowl onto a lightly oiled baking sheet, and slash the top a few times with a very sharp knife. Bake at 220℃ (200℃ fan)/425°F/gas mark 7 for about 50 minutes, until risen and golden. The loaf will sound hollow if you tap it on the bottom when cooked.
Transfer to a wire rack to cool.