Rinse and drain one pound of lentils. Place them into a large saucepan. Pour in five cups of cool water, cover and bring to a boil. Reduce heat to medium-low and simmer for 15-20 minutes or until the lentils are tender. Drain and set off to the side.
In a medium bowl, combine the ketchup, chili powder, cumin, paprika, salt, pepper, water, maple syrup, mustard and vinegar. Whisk to combine and set aside.
Preheat a Dutch oven over medium heat with a tablespoon of olive oil. Once the oil is hot, sauté the peppers and onions together until soft and translucent. Next, add in the minced cloves of garlic and cook for 1 to 2 minutes.
Reduce the temperature to low and pour in the sauce. Stir and simmer for 10 minutes. Add the drained lentils, stir to combine and heat for 5 minutes or until warmed through.
Spoon the lentil sloppy joe filling on a whole wheat slider bun and top with the slaw and serve.
Sloppy joe filling can be kept warm in a crock pot set on low or warm setting.