Soak beans, uncovered, at room temperature, overnight.
In a large pot, place the soaked beans, onion, celery, carrot, garlic, bay leaves and thyme. Cover with cold water. Do not salt water.
Simmer over low heat until tender, about 20 to 25 minutes. Once fully cooked, season with salt, drain well and discard vegetables. Cover beans and cool in the refrigerator.