Preheat the slow cooker if necessary; see the manufacturer's instructions. Heat the oil in a frying pan, add the onion and fry, stirring, for 5 minutes or until lightly browned.
Add the nuts and seeds and fry until lightly browned. Stir in the rice and stock, followed by the dried fruit, spices, bay leaves and tomato purée, then season with salt and pepper to taste. Bring to the boil, stirring.
Transfer the mixture to the slow cooker pot. Cover with the lid and cook on low for 3–3½ hours or until the rice is tender and the stock has been absorbed. Discard the cinnamon, cloves and bay leaves before serving, garnished with extra nuts.