Heat oil in a Dutch oven over medium-high heat. Add the corned beef, fat side down, and sear until the fat is lightly browned, 3-4 minutes. Turn the meat over, sear one minute, and remove from the pan. Add the onion, carrots, bay leaves and garlic and cook, stirring occasionally, until just starting to soften, about 2-3 minutes. Return the corned beef and reserved pickling spice to the pan, fat side up, and add 3 bottles of the cider and enough cold water to just cover. Bring to a boil, reduce the heat to low; cover and gently simmer until tender, 3-3 1/2 hours.