Place the rinsed lentils, sliced carrots, diced onion, and minced garlic into the crockpot.
Add the can of diced tomatoes with its juice and pour the vegetable broth over everything.
Sprinkle in the dried thyme, salt, and black pepper.
Stir the mixture gently to combine the ingredients.
Cover the crockpot and cook on low for 7 hours until the lentils are soft and the carrots are tender.
Stir the soup once more before serving to even out the texture.