Before putting on the stove, zest one of the oranges into a small sauce pot. Juice the zested orange and add to the pot. Juice two additional oranges and add to the pot as well.
Over medium heat, whisk the brown sugar into the pot. Let this reduce until it begins to thicken into a glaze.
Place the ham in a roasting pan. Pour the glaze over the ham and spread it to coat the entire ham. Pour the water into the bottom of the pan. Tent the ham with aluminum foil and bake for an hour.
Cut the fourth orange into thin slices. Remove the foil from over the ham and add the sliced oranges to the bottom of the pan around the ham. Continue to cook for another hour or until it reaches and internal temperature of 150 degrees F/65.5 degrees C. Let rest for 20 minutes before slicing and serve garnished with the sliced oranges.