Place ham in slow cooker.

Mix dry mustard and brown sugar together. Press on ham.

Pour cider vinegar in the bottom of the slow cooker. I don't usually measure this.

Cook on low for 6 hours. Turning the ham over after 2 hours. (If I'm not home I don't worry about this)

After 4 hours of cooking, if desired, you can make another sauce to pour over the ham. In a sauce pan, mix 1 additional cup brown sugar, 1 additional cup cider vinegar and 3 additional Tablespoons dry mustard together. Reduce over medium heat for about 20 minutes. Drain juice in the slow cooker off the ham. Shred the ham into large chucks. Add ham back to slow cooker. Pour the reduced vinegar brown/brown sugar mixture over the ham. Continue cooking shredded ham in the slow cooker for 1 1/2 more hours.

NOTE: If I don't have time I don't make the reduced sauce to pour over the ham. I simply let the ham slow cook in the original sauce. Shred and serve. It's delicious just like that too!