This recipe yielded our best ham results yet: https://www.delish.com/cooking/recipe-ideas/recipes/a58445/best-... :

• 1 (10-lb.) fully cooked whole ham (boneless or bone-in)
• ½ c. packed brown sugar
• ¼ c. Dijon mustard
• 1 tbsp. apple cider vinegar
• 1½ c. apple cider

Preheat oven to 325º. Place ham cut side down on a roasting rack set in a roasting pan and score diagonally.

Cover with foil and bake until warmed throughout, 2 1/2 to 3 hours.

During the last 45 minutes of cooking, make glaze: In a small saucepan over medium heat, whisk together brown sugar, mustard, apple cider vinegar, and apple cider. Bring up to a boil, then reduce to a medium simmer and cook until reduced by half, 10 to 15 minutes.

Brush glaze on ham every 15 minutes, until until an instant-read thermometer inserted in the thickest part reads 140°.

Remove ham from oven and let rest 15 minutes before slicing.