In a small bowl, combine sage, salt, pepper, and garlic. Rub mixture over the roast.
Slow Cooker: Add 1/2 cup water or broth and roast to slow cooker. Cook on low for 6-8 hours.
Instant Pot: Add 1 cup water or broth to Instant Pot and place roast inside. Cook on high pressure for 60 minutes. Let sit for 10 minutes after cook time ends to naturally release, then quick release remaining pressure.
Near end of cooking time, whisk together glaze ingredients in a small saucepan. Bring to a boil, then reduce heat to simmer, stirring occasionally. Simmer until glaze thickens, about 2-3 minutes. Season with salt and pepper, to taste. Keep warm until roast is ready.
Remove roast and shred meat into pieces. Place on a serving platter or plate and pour the glaze over all of the meat, then serve.