Rinse the dried white beans thoroughly under cold water, removing any debris or discolored beans. If you have time, soak them overnight in cold water; otherwise, proceed with unsoaked beans.
Dice the onion and mince the garlic finely. Chop the carrots into small cubes to help them cook down evenly and release their sweetness.
Add the soaked or unsoaked beans, diced onion, minced garlic, chopped carrots, vegetable broth, thyme, bay leaves, and olive oil into the slow cooker. Stir everything together to combine.
Cover the slow cooker with its lid and set it to low. Let it cook for 6-8 hours if beans are soaked, or 8-10 hours if unsoaked, until the beans are tender and the flavors meld. The house will fill with a warm, earthy aroma.
Once the cooking time is up, remove the bay leaves and taste the soup. If needed, season with salt and pepper to your liking. For a creamier texture, mash some of the beans with a potato masher or blend part of the soup with an immersion blender directly in the pot.
Finish by squeezing a splash of lemon juice or vinegar into the soup. Stir well to brighten the flavors and add a pop of freshness. Ladle into bowls and enjoy this comforting, hearty dish.