How to Make It
Stir together sugar, syrup, water, mustard, garlic, thyme, and cloves in a medium saucepan. Bring to a boil over medium. Reduce heat to medium-low, and cook, stirring occasionally to dissolve sugar, 5 minutes.
Place ham, cut side down, in an 8-quart slow cooker. Pour syrup mixture over ham. Cover and cook on LOW until heated through, about 4 hours, using a turkey baster to baste ham with cooking liquid every 45 minutes. Remove ham from slow cooker, and place on a serving platter. Tent with aluminum foil to keep warm.
Pour cooking liquid into a small saucepan. Bring to a boil over high. Reduce heat to medium, keeping mixture at a low boil. Cook, stirring occasionally, until reduced to about 1 1/4 cups, 15 to 20 minutes. Discard garlic, thyme, and cloves. Serve sauce with ham.