In a large bowl, use a wooden spoon to mix together all of the ingredients until a shaggy dough forms. Cover the bowl with cling-film and leave it in a draught-free spot for the next 12-16 hours.
Using a dough scraper - or a gentle hand - tip the dough out onto a lightly floured surface. Using floured hands or a floured bench scraper, gently shape the dough into a ball. Kitty says to transfer the shaped ball to a sheet of parchment paper (I transferred mine to a semolina-dusted banneton), cover with a clean tea-towel, and leave to rise for an hour.
Preheat the oven to max, and have your cast-iron casserole dish & lid on standby. Kitty says to put the casserole dish into the oven to heat up, but I've read horror stories online about things cracking and I love my Le Creuset too much to risk it. You do you.
Uncover the dough, (transfer to parchment paper if you followed my unofficial instructions), and gently lower the dough into the casserole dish. Using a lame or a sharp knife, slash the top of the dough. Place the lid on and bake in the preheated oven for 30-minutes before removing the lid and baking for a further 15ish-minutes, or until the crust is deep golden brown.
Gently remove the loaf from the casserole dish & place on a wire rack. Leave to cool for at least 1-hour before slicing.