Preheat oven to 350 degrees. Trim all but 1/4 inch fat from the ham, and score remaining fat in 3/4-inch diamonds, just deep enough to reach the meat without cutting into it. Place ham, fat side up, on a rack in a roasting pan.
In a small bowl, mix together brown sugar, mustard, and bourbon. Brush 1/4 of the glaze over the ham. Bake the ham, brushing with remaining glaze every 30 minutes, until heated through (140 degrees on a meat thermometer), about 2 hours.
Let ham stand about 15 minutes before carving. Using a knife with a long blade, carve downward to the bone. Run the knife horizontally through the ham, along the top of the bone, to release the slices.
Martha has also prepared this recipe by trimming all but 1/2 inch of fat from the ham in Step 1 of the instructions.