Preheat your oven to 315 degrees.

Place the ham in a roasting pan with the rounded side up.

Pour the ½ cup of water to the pan and tent the ham with tinfoil.

Place the ham in the oven, cooking for roughly 20 minutes per pound (an ideal internal temp would be 145 degrees, be careful of the bone when taking the temp as that could throw off the temp a bit).

With about 30 minutes remaining for the cook time start to make the brown sugar and mustard glaze.

Using a small sauce pan, whisk together the mustard and brown sugar until creamy.

Over medium heat, bring to a low rolling boil, reduce the heat and let simmer until it is both thicker and darker in color.

Remove the ham from the oven and uncover. Pour the brown sugar glaze over the top and then use a pastry brush to make sure it covers the entire surface of the ham.

Return to the oven, this time uncovered.

Cook for roughly another 20 minutes or until the ham is at temp and the glaze has worked its magic.

Let the ham rest for about 20 minutes before cutting.