Place the rinsed lentils, sweet potato pieces, diced onion, and sliced carrots into the slow cooker.
Add the vegetable broth, diced tomatoes with their juice, and minced garlic.
Sprinkle in the cumin, smoked paprika, thyme, salt, and black pepper.
Stir everything once to combine, then cover and cook on low for 7 to 8 hours or on high for 4 hours.
Taste and adjust salt or pepper if needed. Ladle into bowls and top each serving with a sprinkle of fresh parsley.