Defrost the ham if it is frozen. Put the ham in the fridge over night to defrost it.
Take the ham out of its package, and let it breathe for 10 minutes.
Preheat your oven to 325 F (or 160 C).
Wrap the ham in tin foil. Place your ham in a roasting pan.
Put the ham in the oven and bake for 100 minutes and up to 180 minutes.
Make the glaze. Mix the brown sugar, mustard, apple cider, and apple cider vinegar together in a small saucepan.
During the last 45 minutes of baking, open the foil every 10 minutes and brush the ham with the glaze.
When the ham is done cooking, take it out and remove the foil. Let it rest for 10 to 20 minutes before eating it.