1Place a wire rack on a roasting sheet lined with foil.
2Put the ham cut side down in an oven bag and insert a probe thermometer all the way to the center.
3Place ham in the oven at 250 degrees and cook until it reaches 110 degrees (3.5 to 4.5 hours).
4In a saucepan, combine 1/2 cup of water, 1 1/4 cups of sugar, and 3 tablespoons of light corn syrup and cook on medium-high heat for 6-7 minutes without stirring or touching.
5Reduce the heat to low.
6Microwave the apple cider vinegar for 90 seconds until steaming.
7Once the caramel is a light brown color, add the microwaved vinegar, 1/4 teaspoon of five spice, and 1/2 teaspoon of pepper.
8Reduce the mixture to 1 1/3 cup (5-7 minutes).
9Remove the ham from the oven bag.
10Reserve 1/4 cup of the ham juices and glaze the ham with a pastry brush.
11Put the ham back into the oven at 450 degrees for 5-7 minutes until bubbling.
12Remove the ham from the oven.
13Add the reserved ham juices into the remaining glaze and reheat while whisking.
14Serve the ham with the cider-vinegar caramel glaze.