Spray a 6 to 7 quart oval slow cooker with non-stick cooking spray. Remove ham from packaging and place flat side down in the prepared slow cooker.
Melt butter in a small saucepan over LOW heat. Add thyme and simmer for several minutes until golden and fragrant. Add remaining glaze ingredients and stir well to combine. Simmer for another minute or two and then remove from heat and set aside.
Pour glaze over the top of the ham, cover, and cook on LOW for 3 to 4 hours until warmed through. Baste ham with the cooking juices once or twice during the cooking time.
Remove ham from slow cooker. Cover loosely with foil and let rest for 10 minutes. Slice ham and drizzle with some of the cooking juices, if desired.
If you'd like a browned, crispy edge, preheat your oven to BROIL at the end of the ham cooking time. Remove the ham from your slow cooker and transfer it to an oven-safe baking dish or roasting pan. Spoon some of the cooking juices from the slow cooker over the top of the ham and place the dish on a low rack under your oven broiler for a few minutes until ham is nicely browned. Slice and serve as directed.
Note - If you get home from the store to find that your ham is too large and the lid won't fit on your slow cooker, just cover the top of your slow cooker with a sheet of foil (heavy duty works best), covering the ham and crimp it around the edges of the slow cooker.