In a large frying pan over medium heat cook the mince, onion and garlic until brown. Add the passata, tomato puree, salt and oregano and stir until well incorporated. Cook until heated through.
In a large bowl mix together the cottage cheese, grated Parmesan cheese and grated mozzarella cheese.
Spoon a layer of the meat mixture onto the bottom of the slow cooker. Add a double layer of the uncooked lasagne sheets. Break them up if you need to fit them into your slow cooker. Top pasta with a portion of the cheese mixture. Repeat the layering of sauce, pasta sheets and cheese until all the ingredients are used.