Pour entire can of pineapple in bottom of large slow cooker. Place ham on top, flat side down.
In a small bowl, combine syrup, brown sugar, cinnamon, mustard and pepper. Pour over ham.
Set slow cooker to low and cook for 4-5 hours.
Remove ham and keep warm. Skim fat off the top of remaining liquid in slow cooker.
Pour liquid into small saucepan and bring to boil. Reduce heat to simmer, cook until reduced to desired consistency.
Serve sauce on the side or heat oven to broil and glaze ham. Broil 3-4 minutes for a caramelized crust.