Place lentils in a medium saucepan, cover with water, and bring to a boil. Boil for 10 minutes, drain well, and add to the slow cooker.
Combine olive oil, carrots, red onion, tomato paste, garlic, oregano, bay leaves, salt, and pepper in the slow cooker and cover with about 6 to 7 cups of water. Cook on Low until lentils are soft, 6 to 8 hours.
Do not skip the step of pre-boiling the lentils; if you don’t do this, your lentil soup will turn out like sludge.
Source: Read Full Article