Juice two of the oranges and strain the juice through a fine sieve.
Singe the duck legs over a flame to remove any residual pinfeathers.
In a casserole dish or Dutch oven, add the olive oil, the crushed garlic cloves (skin on), and the thyme sprigs.
Add the duck legs and sear until browned on both sides. Season with salt and cover. Cook for about 10 minutes over medium-high heat, then pour in the white wine and the strained orange juice.
Cover and continue cooking over low heat for about two hours. If necessary, add a little water or vegetable broth, a small amount at a time, to keep the pan moist.
To serve, plate the duck legs, spoon over several tablespoons of the cooking pan juices, and accompany with a fresh fennel and orange salad prepared with the remaining ingredients.