For pizza dough, combine yeast and 100ml lukewarm water in a small bowl, stir to dissolve. Add 2 tbsp flour, stir to combine, cover and stand in a warm place until foamy (25-30 minutes). Place remaining flour in the bowl of an electric mixer fitted with a dough hook, add yeast mixture, olive oil, 1½ tsp sea salt and 140ml water, and mix until it comes together. Knead until smooth and elastic (5-8 minutes), divide into four and place on an oiled oven tray. Brush with olive oil, cover and stand in a warm place until doubled in size (45 minutes-1 hour).
Meanwhile, for garlic and oregano oil, cook oil and garlic in a small saucepan over medium heat until garlic is golden (3-4 minutes), add oregano, remove from heat, season to taste and set aside.
Preheat oven to 220C. Process onion and garlic in a food processor until finely chopped. Strain tomatoes, add liquid and half the solids to food processor (reserve remaining solids). Process until smooth, transfer to a saucepan and stir frequently over medium-high heat until thick (10-12 minutes). Remove from heat, add reserved tomato, season to taste and cool.
Place two heavy-based oven trays in oven. Roll out each piece of dough on a floured surface to a 4mm thick rectangle, spread with one-quarter of the tomato mixture, scatter with one-quarter of the sopressa and mozzarella and cook on preheated oven trays until golden and crisp (6-8 minutes). Drizzle with garlic and oregano oil and serve immediately.