Combine sage, salt, pepper and garlic. Rub over roast.
Place in slow cooker with ½ cup water.
Cook on low for 6-8 hours.
About 1 hour before roast is done, combine all ingredients for glaze in small sauce pan. Heat and stir until mixture thickens. Brush roast with glaze 2 or 3 times during the last hour of cooking.
Serve with remaining glaze on the side.
Notes
You can substitute sage with a few things. Poultry seasoning has sage in it, so that will work. Also Marjoram or Rosemary would work. Sage is used sparingly, so you will probably be fine if you don't have any of the spices listed. But these are a few options.
You could also use a pork loin, but the cooking time will be longer because a pork loin is a lot bigger.