Mix the yeast and sugar in the lukewarm water and allow the yeast to activate.
When the yeast is frothy, it’s ready to use.
Sieve the flour into a mixing bowl and add the salt, olive oil and yeast mixture. Mix to a soft, loose dough, adding more flour or water as required. Knead until the dough is very pliable, which should take about 7–10 minutes by hand.
Leave the dough to rise in a well-oiled bowl covered with cling film until the dough has trebled in size and is springy to the touch, which will take 2–3 hours. This will rise best in a warm, draught-free place, e.g. a hot press or near a cooker or oven.
When it has risen, knock it back and place onto a lightly floured surface. Knead it again by hand for 2–3 minutes.
Roll out the dough to a 33cm x 28cm rectangle about 5mm–1cm thick.
Spread the dough with tomato sauce and sprinkle over the mozzarella, pancetta, olives and a little of the thyme.
Roll up like a Swiss roll, tucking in the ends. Transfer to a lightly oiled baking sheet with the join underneath. Cover with a damp cloth and leave for 30–45 minutes in a warm, draught-free place.
Preheat the oven to 200°C/400°F/Gas 6
Remove the cloth and pierce the roll with a large fork about 5 times, through to the baking sheet. Lightly brush the surface with olive oil and sprinkle over the sea salt.
Tuck the remaining thyme sprigs into the surface of the dough.
Bake for 30–35 minutes, until cooked through and pale golden. Drizzle over a little extra virgin olive oil and transfer to a wire rack to cool.