Preheat the oven to 350. Set up your mise en place, ie.; your sauce, your meatballs that have been sliced, your sliced mozzarella, your parmesan cheese, your lasagna sheets.
I used a 9 1/2 x 9 1/2 square pan, however; you can double the recipe and use a rectangular pan of your choice. Cover the bottom of your pan with about 1 cup sauce and put your first layer of pasta sheets overlapping a little as shown in the picture.
Cover with about 1/3 to 1/2 of the ricotta mixture (depending how many layers you are making). Add your sliced meatballs.
Top with your mozzarella.
Add 3/4 cup to a cup of the marinara sauce and spread evenly over the cheese.
Repeat the layers, layering your pasta sheets in the opposite direction ending with just a final lasagna sheet, topped with sauce and your parmesan cheese.
Cover with lightly oiled foil and cook for about 45 minutes until puffed up and bubbling.
At this time uncover the lasagna and cook an additional 15 minutes. Let the lasagna rest for about 15 minutes before you cut into squares.
At this point I like to cut into squares and put in individual single serving dishes, top with mozzarella, put under the broiler and melt the cheese and let it get a little brown on top. Bon Appetite!