Season the scaloppini evenly with 4 1/2 teaspoons salt.
Place the flour in a shallow bowl, the eggs in a separate shallow bowl and the breadcrumbs in a third shallow bowl. Season the breadcrumbs with the oregano, pepper flakes and remaining 1 1/2 teaspoons salt. Working with one piece of turkey at a time, dredge each piece in the flour, followed by the egg and finished with the breadcrumbs. Place on a baking sheet.
Heat a large skillet over medium-high heat. Place a wire rack on a baking sheet. Add 1/4 cup of grapeseed oil to the hot skillet. Fry the turkey pieces, 2 at a time or as many as will fit in your skillet, until golden brown and crispy, about 3 minutes per side. Add more oil to the skillet as needed. Remove to the rack and continue with the remaining turkey pieces.
Preheat the oven to 400 degrees F. Butter an 11-by-13-inch roasting pan.
Spoon 1 cup of marinara on the bottom of the prepared pan. Nestle the turkey pieces in the sauce to make one layer covering the bottom of the pan, about 4 pieces. Spoon another cup of sauce on top and sprinkle with 1 cup mozzarella and 1/2 cup Parmesan. Sprinkle half of the basil over the top. Shingle another layer of turkey, sauce, cheese and basil. On the final layer, cover the top with the remaining turkey and spoon over the remaining sauce. Sprinkle with the remaining 1 1/2 cups mozzarella and 1/2 cup Parmesan. Bake until golden brown and bubbly, about 45 minutes. Allow to rest for 10 minutes before slicing and serving.