What you'll do is just layer, layer, layer. Little bit of (store-bought!) marinara down in the bottom of a big cast-iron skillet (I used a 13-incher for this). Then goes a layer of the cooked, broken lasagna sheets. Then some shredded chicken. Then a few dollops with the herbed ricotta. Followed by shredded mozzarella, and then more sauce. Repeat about three more times. It doesn't have to be perfect, because a) life and b) you'll top it all with the remaining sauce and more shredded cheese.
Bring a large pot of salted water to a boil. Cook the noodles, covered, until tender, about 4 to 5 minutes or according to package directions. Drain the noodles and toss with 1 tablespoon oil in a medium bowl.
Combine the ricotta, parsley, lemon zest and a pinch of salt in a medium bowl.
Spoon about 2/3 cup marinara in the bottom of a large 13-inch cast-iron skillet. In a single layer, arrange about a third of the cooked lasagna sheets over the sauce. Sprinkle about a third of the chicken over the noodles, followed by five to six dollops of the herbed ricotta mixture and about a third of the mozzarella. Repeat two more times for a total of three layers, or until everything is in the skillet.
Bake uncovered for 30 minutes. Flip the oven to broil and bake until the cheese is browned and bubbly, about 5 minutes. (Don't walk away! It happens fast.)
Let the lasagna rest about 10 minutes. Garnish with the Parmesan and parsley leaves.
The key here is to let it sit! If you cut right into it immediately, the sauce will be on the runny side. But if you let it rest, it gives the pasta time to soak up the marinara.