In the base of a large slow cooker, combine 1 cup lentils, 2 cups of vegetable broth, 8 ounces tomato sauce, 6 ounces tomato paste, 1 minced onion, 1 diced bell pepper, ½ tablespoon soy sauce, 1 tablespoon minced garlic, 2 tablespoons maple syrup, 1 tablespoon red wine vinegar, 1 teaspoon kosher salt, and ½ teaspoon pepper. Stir until everything is evenly combined.
Place the lid on the slow cooker and set to cook on high for 4 hours or on low for 8 hours.
After slow cooking, stir the lentils into the sauce again. If needed, leave the lid off the slow cooker for 5 minutes to thicken up (I typically don't find this necessary).
Serve the lentil sloppy joe mixture on buns or as desired.
