Preheat oven to 375 degrees Fahrenheit.  Spray a 9 x 13" pan with non-stick cooking spray.

In a 12"frying pan, brown the ground beef.  Drain liquid.  Add the jar of marinara sauce and cook until heated through.  (If you aren't using meat, skip this step.)

In a medium bowl, mix the ricotta, egg, Parmesan cheese, oregano, Italian spice, and salt.   

Begin layering by spreading a little sauce in the bottom of the pan.  Place three lasagna pieces on top, next, spread 1/3 of the ricotta mixture over the noodles, sprinkle 1/4 of the mozzarella cheese, end by spreading more sauce.  Do this two more times and end with a layer of noodles and sauce. Finally, sprinkle with remaining mozzarella cheese.

Cover with foil and bake for 30 minutes.  Uncover and bake for an additional 5-10 minutes or until the cheese is melted and the noodles are tender when poked with a fork.  Depending on how far ahead of time you prepare the lasagna, your cooking time will change.  I would expect to add an additional 15-20 minutes uncovered if you make the lasagna and bake it right away.

You can also use this recipe for regular lasagna noodles.  Just follow the package instructions to boil them and then use these same instructions to layer.  Bake uncovered for 30 minutes at 350 degrees Fahrenheit.