Remove your ham from the fridge, 30 to 45 minutes before cooking.
Preheat your oven to 275 degrees
Remove the ham from the packaging. Set the glaze packet aside.
Place the ham onto a sheet pan or roasting pan with the widest part on the bottom.
Insert the probe of a thermometer into deepest part of the meat being, careful not to hit any bone.
Cover the ham with heavy duty foil tightly, making sure not to mess up your probe.
Put the ham into the oven.
Attach the probe to the thermometer base. Set to go off at 128 degrees. Plan on 3-4 hours for it to reach that temperature.
When the ham is almost at 128, take the contents of the glaze packet and pour into a pot. Add 3 tablespoons of water, mix to combine. Bring to a boil and then remove from the heat.
Remove the ham from the oven. Turn the oven up to 400 degrees.
Take the foil off. Leave the probe in. Brush the glaze all over the ham.
Put the ham back in the oven and cook until the internal temperature reaches 137 degrees. There will be enough carryover heat for the ham to pass the 140 degree mark.
Allow to rest for 15-20 minutes and then serve.