Preheat the oven to 350 degrees.
In a small saucepan, combine the brown sugar, orange juice and dijon and bring to a boil. Simmer until it begins to thicken.
In a oven safe dish, add the ham in and gently separate the sliced pieces. Pour the mixture over the ham, evenly coating it. Try to get the sauce between the slices as wel.
Cover with foil and cook for about 45 minutes until warmed through. You can also baste it with the juices throughout. Remove the foil and let brown a bit.
Remove and serve!