Braised pork belly with borlotti beans

Name: Braised pork belly with borlotti beans
Ingredients: 800g skinless, boneless pork belly cut into large chunks, or 800g pork belly slices; 1 tbsp plain flour; 2 tbsp olive oil; 1 large onion finely chopped; 2 carrots finely chopped; 2 celery sticks finely chopped, any leaves reserved and chopped, to serve; 1 rosemary sprig; 2 bay leaves; 2 garlic cloves roughly chopped; 1 tbsp tomato purée; 200ml white wine; 500ml chicken stock; 2 x 400g cans borlotti beans drained; large handful of parsley leaves picked and finely chopped, to serve; 1 lemon zested, to serve