Source: Martha Stewart Recipes
adapted by http://theresalwaysthyme.blogspot.com
1 (18-pound) whole bone-in, fully cooked, smoked ham, room temperature (I used a much smaller ham)
1/2 cup champagne vinegar
1 cup maple syrup
2/3 cup country-style Dijon mustard
2 tablespoons apricot jam (I used more, about a 1/4 cup)
pinch of coarse salt
freshly ground black pepper
Preheat oven to 350 degrees. Line a roasting pan with heavy-duty aluminum foil.
Rinse ham under cool running water. Pat dry and wrap with parchment paper-lined aluminum foil; place in prepared roasting pan. Transfer to oven for 4 1/2 hours.
Meanwhile, in a small saucepan, heat vinegar over medium-high heat until reduced to 2 tablespoons, about 6 minutes. Add maple syrup, mustard, jam, and salt; season with pepper. Cook, whisking, until well combined, about 2 minutes. Set glaze aside.
Remove ham from oven and uncover. When cool enough to handle, cut off rind using a sharp knife. Slice off most of the fat, leaving a 1/4-inch-thick layer. Score fat on top of ham in a pattern of 1- to 2-inch diamonds.
Brush ham evenly with one-third of the glaze and return to oven. After 20 minutes, brush ham again with half the remaining glaze. Cook for 15 minutes and brush with remaining glaze. Continue baking ham until an instant-read thermometer inserted into thickest part of ham reaches 145 to 150 degrees, about 15 minutes more.
Transfer to a cutting board. Let ham cool 30 minutes before carving.