Place the lentils, onion, carrots, garlic, ginger, curry paste, broth, and salt directly into the slow cooker.
Stir everything together until the curry paste is evenly distributed.
Cover and cook on low for 6 to 8 hours, until the lentils are soft.
Stir in the coconut milk during the final 30 minutes of cooking.
Turn off the heat and add the lime juice. Taste and adjust salt if needed.
Ladle the soup into bowls and finish with chopped cilantro.