Rub the duck legs all over with the split garlic cloves and put them in a glass bowl with the salt, pepper, bay leaves, and thyme. Cover with a tea towel and refrigerate overnight or up to 48 hours, turning once.
Heat the oven to 200 degrees F. Rinse the duck and pat dry with a towel. Set the legs in a baking dish and tuck in the garlic cloves. Pour over enough fat to cover them, place over heat and when you see the first bubble, set it on a rimmed baking sheet in the oven and bake uncovered until the meat is very tender and shrinks away from the bone, about 4 hours. Cool slightly in the fat, then carefully lift them out.
While the confit cooks, soak 2 wooden skewers in a saucepan and boil 5 minutes to sterilize. Lay in the bottom of two sterilized glass loaf pans (breaking the sticks if needed). Lay on the duck legs and ladle over the fat, leaving any juices behind. Make sure they are well covered. Cover with foil or plastic wrap, and refrigerate a week to mellow.
To cook, remove the pans from the fridge and set in simmering water about 20 minutes, so you can pull the legs out without breaking. Heat the oven to 350 degrees F and lay the legs skin-side down with a little fat around them in a cast iron pan. Bake until hot, about 15 minutes. Remove and turn oven to broil. Turn legs skin-side up and broil to crispen skin, about 3 minutes.