Pour out the tomatoes into a medium bowl; add garlic, oregano, 1.2 tsp salt, and ½ tsp pepper, mix well.
In another medium bowl, combine Parmesan and ricotta with parsley and ¼ tsp pepper.
Pour 1/3 cup of tomato mixture on the bottom of the slow cooker pot. Cover with a layer of noodles (you can break them, if necessary). Spoon half of the ricotta mixture evenly over the noodles. Add another layer of tomato mixture – a third of what is left. Sprinkle with one-third of grated mozzarella. Cover with one more layer of noodles, spread the remaining ricotta mixture evenly over the noodles, cover with the rest of the tomato mixture and sprinkle with the remaining mozzarella.
Set the slow cooker to low. Cover the pot and cook for 2 to 3 hours, until the noodles are soft.
You can cook this lasagna recipe in a large covered casserole an oven at 375° F/190° С/ Gas Mark 5 for 50 minutes to 1 hour. The only thing you have to change is dry lasagna noodles – replace them with no-boil ones.