1: Put the flour in a mixing bowl and make a well in the centre. Add the yeast, sugar and 100ml (3 1/2fl oz) warm water. Gently mix with a fork and leave for a few minutes, until the yeast has dissolved and starts to foam.
2: Add another 150ml (1/4pt) warm water, the olive oil and 1 tsp flaked sea salt, stirring until the mixture forms a sticky dough. Knead for 5-10 minutes, adding a little extra oil if needed, until smooth and elastic. Shape the dough into a disc and transfer to a large, oiled bowl. Cover with a damp tea towel and set aside somewhere warm for 1 hour, or until doubled in size.
3: Meanwhile, preheat the oven to gas 6, 200°C, fan 180°C. Wrap the garlic bulb in kitchen foil, ensuring it is tightly sealed. Roast directly on the oven shelf for 25-30 minutes, or until tender. Once cool enough to handle, gently squeeze out the cloves and set aside, until needed.
4: Put the tomatoes in a bowl and drizzle with oil. Toss to coat, then season and set aside, until needed.
5: Lightly grease a deep 20cm x 30cm (8in x 12in) roasting tin with oil. Tip the dough into the tin and stretch it out to fill the edges and corners. Using oiled fingers, make rows of evenly spaced dimples over the surface of the dough and press in the garlic cloves and tomatoes. Scatter over the rosemary. Cover with oiled clingfilm and set aside to prove for a further 45 minutes, or until doubled in size.
6: Preheat the oven to gas 6, 200°C, fan 180°C. Scatter the remaining sugar and a little sea salt over the dough. Put a separate tin in the bottom of the oven and carefully fill with boiling water from the kettle. Bake the dough on the middle shelf for 30 minutes, or until golden. Leave to cool in the tin for a few minutes. Drizzle with a little more oil before serving.