To prepare the dough

1. Put the flour, salt and tepid water in a stand mixer fitted with the dough hook and mix on a slow speed for 4-5 minutes. Increase the speed to medium and mix for a further 10 minutes. Add the starter and mix on a slow speed for 1 minute then on medium speed for a further 15 minutes. Your dough should be soft and elastic: open a small piece to see the structure -- it should hold together well.
2. Put the dough in an oiled bowl, measuring about 9 inches (23cm) across the top, cover and leave to rise until at least doubled in size. This will take around 8 hours in the summer, but allow 9-10 hours in a cooler kitchen during the winter.
3. Carefully tip the dough out onto a floured surface and begin to stretch the outside edge into the middle -- don't push too hard, you want to keep as much air in the dough as possible. Rotate the dough 90 and repeat. Continue in this way until you've gone around the dough a few times, then turn it over gently. Push a plastic bench scraper underneath, rotate the dough 90 and repeat several times. This action will tighten the top of the dough and smooth it off. (video)
4. Put the dough in a floured banneton or in the middle of a long piece of parchment paper (which makes it easier to lift the dough into the pan). Leave to rest for a further 1-2 hours.
5. Heat your oven to 450°F and put a heavy-based ovenproof saucepan with a domed lid inside to heat up for 10 minutes.
6. If using a banneton to shape the dough, put a large sheet of parchment paper over the top of it and carefully invert the dough onto the paper.
7. Protecting your hands with oven mitts bring the hot pan over to the dough. Using the parchment paper, carefully lift the dough into the hot pan and tuck it down around the sides. Cut off the excess paper.
8. Using a very sharp blade, cut a deep cross or hashtag in the top of the dough. Put the lid on the pan and put in the oven. Bake for 25 minutes, then remove the lid and bake for a further 30 minutes until well browned.
9. Lift your sourdough out of the pan and put on a wire rack to cool for 2 hours before eating. Delicious eaten freshly baked, the sourdough is also excellent toasted and makes a great base for bruschetta.