Place the sausage links in your slow cooker in an even layer.
In a medium bowl, whisk together the maple syrup, brown sugar, Dijon mustard, soy sauce, garlic powder, and black pepper until well combined.
Pour the maple mixture over the sausages, stirring gently to coat all the links evenly.
Cover and cook on LOW for 3-4 hours or HIGH for 1.5-2 hours, stirring occasionally.
During the last 30 minutes, remove the lid to let the glaze thicken, stirring every 10 minutes.
Serve warm directly from the slow cooker on the "warm" setting with toothpicks for easy grabbing.