Spray the inside of a slow cooker with cooking spray. Remove ham from packaging and place in slow cooker. (If the ham doesn't as is, you can cut it to make it fit.)
Make the glaze by combining the brown sugar, dijon, and apple cider vinegar in a small bowl. Pour over the ham. Cook ham at low heat for 3-5 hours or until thermometer reads 140 degrees. Let the ham rest for 10 minutes before slicing. Pour on glaze from the slow cooker.
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Notes
Got leftover ham? Go to https://thisdelicioushouse.com and search "leftover ham" for some great recipes!