Slow roasting a ham allows you to imbue it with different flavors, which seep into the meat as it cooks. This keeps the ham moist, preserving its natural flavor and maintaining its texture. The amount of time it takes to safely roast a ham depends on its size and the type of ham you're roasting, so calculate your roasting time a few days in advance. This ensures that you have adequate time to thaw and roast your dish, giving it the best possible quality when it's finished.
Thaw your ham ahead of time. While you can slow roast a frozen ham by increasing your roasting time by about 50 percent, this may compromise its texture, making it tough and chewy. Transfer your roast from the freezer to the refrigerator so it can thaw. This process can take as few as three hours per pound, but the bigger the roast, the longer it takes, so give yourself plenty of time. It can remain in the refrigerator for three to four days after thawing, so don't worry about giving it too much time to defrost.
Unwrap your ham and place it in a roasting dish. The roasting dish should be sized according to the size of your ham, leaving only a few inches between the ham and the sides of the dish.
Preheat your oven to 325 degrees Fahrenheit for raw fresh ham, or 140 F for cooked ham.
Pour liquid into the bottom of the dish. As your ham roasts, it absorbs both the moisture along with any flavor of the liquid, so different recipes call for different types – a combination of water and citrus juice is a common choice.
Cover the roasting pan in aluminum foil, sealing it tightly. Place it in the oven on the lowest rack.
Roast the ham until it reaches an internal temperature of 145 F. The time it takes depends on the type of ham. For example, a whole, smoked, bone-in uncooked ham weighing 14 pounds can take 20 minutes per pound to roast, while a half, bone-in, fresh ham can take up to 40 minutes per pound.
Remove the ham from the oven. Once it's internal temperature is 145 F, it is either ready to carve and eat or ready to glaze. If you are glazing the roast, score the surface of the ham in a criss-cross pattern with a large knife. The cuts should be about 1/4-inch deep and 2 inches apart from each other.
Glaze your ham by pouring your glaze over its skin. The scores you cut into its surface allow it to absorb the glaze more easily. Return the ham to the oven uncovered for 15 to 30 minutes, or until the glaze is dark and bubbling.
Remove the roast from the oven and transfer it to a cutting board. Per USDA guidelines, allow it to sit for 3 minutes before carving and serving.