Place the maple syrup, bourbon, orange juice, dijon and whole grain mustard (if using) into a small sauce pan and whisk to combine. Bring to a boil over medium heat, then reduce the heat to medium and cook for 5-10 minutes or until thickened.

Pour the water into the slow cooker. Unwrap the ham, spread the slices apart and place in the slow cooker cut side up.

Pour the glaze over the ham and in between the slices. Only use half of the glaze here if you'd like a sticky sweet exterior on your ham (see notes). Cover and cook on low for 2 1/2 – 3 hours or until warmed through (about 140 degrees), basting from time to time when you think about it. Slice, serve and enjoy!