Somewhat notional recipe based on an older recipe we're not really using anymore. Makes one 9x12 pan, which is a lot.

Ingredients
1 box (or less) lasagna noodles (preferably oven-ready)
~ 4 cups marinara sauce, thinned with water (required for oven-ready)
~ 4 cups shredded mozzarella
~ 2 cups shredded parmesan or mixed Italian cheeses
~ 16 oz ricotta, mixed with a pinch of nutmeg
Large bag spinach or 1/2 lb loose Italian sausage or extra 8 oz ricotta (choose one of these for an entire tray's worth of one "flavor," or use a third of each to make a split "Neapolitan" style lasagna)

Assembly
Sauce
Noodles
Ricotta
Spinach and/or sausage and/or extra ricotta
More Sauce
Mozzarella
Parmesan/Italian cheese
Noodles
-- Repeat --
Finish with sauce and mozzarella/parmesan on top of last layer of noodles

Preparation

At this point, you can either freeze or cook the lasagna.

To freeze, cover with tin foil and then wrap with plastic wrap before putting into freezer.

To bake, cover with tin foil and preheat oven to 350 degrees.
Bake for 25 minutes covered, then an additional 25 minutes uncovered.
Cool for at least 10 minutes (preferably longer) before serving to allow to set up.

If frozen, defrost completely before cooking or be prepared to cook it for a lot longer.