In a large bowl, stir all the ingredients to a very soft dough. I like to add a bit of old bread dough from the restaurant for added sourness, but you could leave it out or use a sourdough starter/discard.
Give the dough a vigorous beating with your hand for 30 seconds. Cover and leave for 30 minutes.
Drizzle a few tablespoons of olive oil over the top of the dough and on top of your workbench, and rub liberally.Flip the dough on to it, using a scraper to gently pull the dough away from the bowl. Pull the dough into a 30cm or so rectangle, fold in by thirds and then a second time. Return to the bowl for 30 minutes.
Line a baking tray with nonstick paper and rub a little olive oil over it.
Heat the oven to 225°C/fan 200°C.
Place the dough at the centre of the prepared tray, and repeat the stretch and fold of the dough. With the tips of your fingers pointing straight down, dimple the dough about a dozen times, then leave for 30 minutes.
Stretch out the dough again to cover the tray. Sprinkle flaky sea salt over the top. reduce the oven temperature to 200°C/fan 180°C and bake for 25-35 minutes, until golden.
Allow to cool on a wire-rack.