Rinse the dry green or brown lentils in a fine mesh strainer under cold water and quickly pick out any tiny stones or odd-looking pieces.
Rinse your vegetables and dice them. Try to keep them similar in size if possible.
Take out your slow cooker and place it on your table.
Add your chicken breasts first at the bottom.
Add the lentils, diced onion, diced carrots and diced celery on top of the chicken.
Add the minced garlic, cumin, smoked paprika, salt and black pepper.
Pour in the can of diced tomatoes and all of the chicken broth.
Mix everything on top.
Cover and cook on LOW for 6–8 hours or on HIGH for about 4 hours, until the lentils are tender and the chicken shreds easily with a fork.
Once it's done, carefully remove the chicken breasts from the slow cooker and place them on a plate or cutting board.
Shred the chicken with two forks into bite‑sized pieces.
Add the shredded chicken back into the slow cooker and mix everything together.
Taste and adjust the salt, pepper or spices if needed.
Serve your soup hot or portion in meal prep containers.