Heat the oven to 400°F. Trim the zucchini and slice lengthwise into planks about 1/4 inch thick.

Lay the planks on paper towels, sprinkle with 1 teaspoon of the salt, and let them sit 15 minutes. Blot dry, arrange on two parchment-lined sheet pans, brush lightly with the olive oil, and roast 10 minutes. Lower the oven to 375°F.

While the zucchini roasts, brown the ground beef in a large skillet over medium-high heat, breaking it up, about 8 minutes. Drain any fat. Add the minced garlic and cook 30 seconds.

Stir in the crushed tomatoes, tomato paste, Italian seasoning, red pepper flakes, and remaining salt. Simmer uncovered 10 minutes, until very thick.

In a bowl, mix the ricotta, egg, and half of the parmesan until smooth.

In a 9x13-inch baking dish, spread a thin layer of meat sauce. Add a layer of zucchini, half the ricotta mixture, a third of the sauce, and a third of the mozzarella. Repeat once, then finish with the last zucchini, the remaining sauce, mozzarella, and parmesan.

Cover with foil and bake 25 minutes. Uncover and bake 15 to 20 minutes more, until bubbling and browned.

Rest at least 15 minutes before slicing. Top with torn basil and serve.