Brown onions mince and garlic in a saucepan (can do the sauce in a slow cooker instead, I'd suggest to do it overnight) add tin tomatoes tomato paste stock bay leaves and salt and pepper bring to the boil and simmer until thickened (about 1/2-1 hour)
Once your sauce is thickened then you can assemble your lasagna in your slow cooker
Add a layer of sauce then pasta then pour some of your cream till pasta is covered about .5cm to 1cm thick
Then add a decent helping of grated cheese over top add pasta and repeat the process until slow cooker is full, ending with cheese on top