1 1/2 Cups Marinara Sauce (no sugar added), about half of a 24-ounce jar
6 Basil Leaves, cut into thin ribbons (chiffonade)
Line a rimmed baking sheet with parchment paper. Trim the 3 eggplants and slice lengthwise into 1/4-inch thick planks. Arrange on the prepared baking sheet in a single layer and sprinkle liberally with the 1 tsp. sea salt. Let stand for 15 to 30 minutes. You should see tiny moisture bubbles on the eggplant's surface. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 400 degrees.
Pat the eggplant slices dry with paper towels to get rid of the moisture and salt. Lightly brush the eggplant with the 1 Tbsp. olive oil. Roast until just starting to become pliable, 15 to 20 minutes. Meanwhile, beat the 1 egg in a medium bowl. Add the 15 ounces ricotta, 1 tsp. dried oregano, 1/2 tsp. black pepper, 1 cup of the mozzarella cheese, and 1/4 cup of the Parmesan cheese. Stir to combine.
Remove the eggplant from the oven. Reduce the oven temperature to 375 degrees.
Spread about 1/4 cup of the marinara sauce on the bottom on a 9x13 inch baking dish. Arrange about 6 eggplant slices on the sauce (it's okay if they overlap a little). Dollop 1/3 ricotta mixture on top and gently spread it across the eggplant, followed by a thin layer of marinara. Repeat with 2 more layers of the eggplant, ricotta mixture, and marinara. After the final layer of marinara, sprinkle the lasagna with the remaining 1/2 cup mozzarella and 1/4 cup Parmesan.
Cover the baking dish tightly with aluminum foil. Bake for 20 minutes. Uncover and continue baking until the cheese is golden brown and bubbly, 15 to 20 minutes more. Let stand at least 15 minutes before serving. Garnish with fresh basil.