Place lentils in a bowl and cover with cold water. Let them soak for 2-4 hours. This will help them cook more quickly.
Once lentils are soaked, drain them with a colander. Set aside.
In a large pot, over medium heat, add olive oil. Once olive oil is heated through, add onion, carrots and celery. Season with salt and pepper.
Let them cook until tender, about 5 minutes.
Add the lentils to the pot, along with the bay leaves.
Give everything a good stir, and add the vegetable stock - start with 3 cups, and add more if needed.
Let lentils simmer until they are cooked. This can take anywhere from 15-40 minutes, depending on the lentils you are using.
If you run out of vegetable stock and need more, you can add water. Season with salt and pepper.
Optional step - toast the sliced bread in the oven at 400F for approximately 15 minutes, or until hard. You want the bread to be hard, because it will be softened by the soup.Place the toasted bread at the bottom of a soup bowl. Drizzle bread with olive oil and chili flakes. Top the bread with the lentil soup. The bread will absorb the soup and become soft.
Top the soup with more olive oil and chopped parsley. Enjoy!