In a 9×13 baking pan (or pan with a 2 inch ridge), place the ham in it with about 1/2 cup water (so it doesn’t burn to the pan)
In a bowl, stir together the mustard, brown sugar and brown mustards.
Cover the ham with aluminum foil and place in the oven.
Let the ham cook for about 1 1/2 hours and then remove from the oven. Take the mustard mix and use a silicone brush to put it on the ham, inbetween the slices..
If easier, use a fork pulling each slice apart. You can also slowly pour onto the ham.
Put the ham back into the oven uncovered and bake for 30 more minutes, glazing 1 to 2 more times.
Cook until the center is 140℉ (precooked) or 145℉ if not precooked.
Remove and slice your ham and serve on a platter with your sides.