Remove ham from packaging and discard plastic disk covering bone. Place ham in oven bag. Tie closed and cut 4 2" slits in top of bag. Transfer bagged ham to large roasting pan and let stand at room temp for 1 1/2 hours.
Adjust oven rack to lowest position and heat oven to 300 degrees. Bake ham until internal temp reaches 100 degrees, 1 1/2- 2 1/2 hours.
Meanwhile, bring apple jelly, 1/2 c brown sugar, syrup, mustard, cinnamon, and nutmeg to boil in saucepan. Reduce heat to low and simmer, stirring often, until mixture is very thick and reduced to 1/3 cup, about 45 minutes. Remove cinnamon pieces; off heat whisk in butter.
Combine remaining brown sugar and dry mustard in small bowl. Remove ham from oven and let cool 5 minute Increase oven temp to 400 degrees. Cut open oven bag and roll back. Using a pastry brush, paint ham with glaze. Carefully press sugar mixture onto exterior of ham with hands. Return to oven and bake until dark brown and caramelized, about 20 minute Transfer ham to cutting board, loosely tent with foil, and let rest 15 minute
TO CARVE: With ham on its side, cut around the bone with a paring knife to free the attached slices. Switch to a carving knife and slice horizontally above the bone to remove the entire section. Turn ham to cut side down and slice down along the bone to remove the remaining meat. Carefully cut between the slices to separate them.
TO MAKE A PEACH GLAZED HAM: Replace apple jelly with 12 oz peach preserves, dark brown sugar with 3/4 c light brown sugar, and maple syrup with peach schnapps. Omit whole grain mustard, cinnamon, and nutmeg, and add 1/8 t cayenne to glaze. Sub additional 1/8 t cayenne for dry mustard to sugar coating.