Mix the flour, salt and yeast in a bowl. Add the water and oil, knead to form a soft, smooth dough. Cover and leave to rise at room temperature for approx. 1 hr. until doubled in size. On a lightly floured surface, roll out the pastry to approx. 5 mm thick. Cut out circles approx. 10 cm in diameter.
Spread the tomato puree over the circles of dough and top with mozzarella, diced bacon and oregano.
Fold the dough twice, to create corners. Lay the pieces of dough closely together on the prepared tray, tips facing down.
For approx. 30 mins. in the bottom half of an oven preheated to 200°C.