Dry the ham and bring to room temperature.
Preheat the oven to 375 degrees F.
Trim the ham skin, leaving the fat intact.
Score the fat in a crosshatch pattern.
Put the ham flat-side down on a rack in a roasting pan; add 1 cup water.
Bake on the lowest oven rack for 40 minutes, adding more water if the pan gets dry.
Meanwhile, make the glaze: Whisk jam or marmalade with brown sugar, dijon mustard, cider vinegar, and Worcestershire sauce.
Brush the ham with half of the glaze; cover loosely with foil and bake for 45 more minutes.
Brush with the remaining glaze and bake, uncovered, until the glaze is browned, for 40 to 50 more minutes.
Let rest 15 minutes before carving.
