In a large skillet, heat the olive oil over medium heat. Add the onion, carrots, and celery and sauté for 5-7 minutes, or until the vegetables are soft.

Add the garlic and sauté for an additional minute.

Add the lentils, thyme, oregano, and vegetable broth to the skillet. Stir well to combine.

Transfer the mixture to a slow cooker and cook on low for 6-8 hours, or high for 3-4 hours.

Once the soup is ready, remove it from the slow cooker and use an immersion blender to blend until smooth. Alternatively, you can transfer the soup to a blender and blend until smooth.

Season the soup with salt and pepper to taste.

Serve the soup hot, garnished with fresh parsley if desired.