Provencal Vegetable Tian

Name: Provencal Vegetable Tian
Ingredients: 6 tablespoons extra-virgin olive oil, divided; 2 cups thinly sliced leeks, white and pale-green parts only, rinsed well (1 large leek); 1 Yukon Gold potato (8 ounces), sliced 1/4 inch thick; Coarse salt and freshly ground pepper; 1 small eggplant (12 ounces), trimmed and sliced 1/4 inch thick; 1 large zucchini (8 ounces), sliced 1/4 inch thick; 3 large beefsteak tomatoes, sliced 1/4 inch thick; 1/4 cup pitted Kalamata olives, pitted and roughly chopped; 2 teaspoons fresh thyme leaves, divided, plus more for garnish