Add all the ingredients except the liquid smoke to a slow cooker. Mix together and cook for 8 hours on low or 4 hours on high.
Once done, check that the liquid has all been absorbed and the lentils are cooked through. This may vary depending on your slow cooker. If not done, cook for another 30-60 minutes or until the lentils are cooked through and the mixture is thick.
Once done, add the liquid smoke and stir together. Season with additional salt and black pepper to taste. Optionally, use a potato masher to mash the mixture a few times if you prefer it is thicker.
Serve on hamburger buns with coleslaw (if desired) and enjoy!
