Preheat the oven to 200°C (400°F) and line a baking sheet with parchment paper. Toss the diced eggplant with a generous sprinkle of sea salt and let it sit for 10 minutes. Rinse in a colander, dry thoroughly with a kitchen towel and spread on the baking sheet. Toss with 1 tbsp olive oil, salt and pepper and roast in a single layer until tender and slightly browned, about 20 minutes. Heat the remaining oil in a large, deep skillet over medium heat. Sauté the garlic for 30 seconds until fragrant, then stir in the chili flakes and oregano. Add the crushed tomatoes and stock, bring to a boil, then lower the heat and simmer for 30 minutes. Meanwhile, cook the pasta according to package directions and drain. Stir the roasted eggplant, chopped olives and torn basil into the sauce, toss with the pasta and garnish with extra chopped basil.