Finely shave about a teaspoon of zest from the lemon using a very fine grater, taking care to only remove the yellow part of the skin. Combine the zest with 2 teaspoons of Maldon salt and keep in an airtight container until needed.
Remove the halibut portions from the refrigerator about a half hour prior to cooking, and pat them dry with paper towels. Season them liberally with kosher salt. Allow the halibut to rest on a plate outside of the refrigerator, tempering while you prepare the remaining ingredients.
Once all of the vegetables are cut, heat the All-Clad TK 5 Qt. Sauce Pot over medium heat. Add the olive oil followed by the leeks, fennel, and carrots. Stir in a teaspoon of salt and sweat the vegetables for about 2½ minutes. Stir in the garlic and continue to sweat until the vegetables begin to wilt and become tender. Add the white wine and bring it to a boil to cook off the alcohol. When the alcohol is vaporized, reduce the heat, bringing the liquid to a gentle simmer. Stir in the olives, then carefully arrange the halibut on top of the vegetables.
Cover the pan with the lid and cook for about 7 minutes or until the halibut feels firm and resilient but not hard.
Remove the halibut from the pan, then stir the basil into the vegetables. Divide the vegetables and liquid between 4 shallow bowls. Place a piece of halibut on top of the vegetables and drizzle with extra-virgin olive oil. Sprinkle the fish with some of the lemon salt and serve.