In a large, heavy-bottomed pot, heat oil over medium heat. Add bacon and render fat (fry) until crispy, about seven minutes. Add garlic and carrots and sauté until soft, another four minutes.
Add beans and thyme springs to pot; add enough water to cover the beans by at least 4 inches and bring to a boil.
Turn down heat and simmer beans for anywhere from 45 minutes to 1.5 hours, until beans are just falling apart.
About 20 minutes before, add salt and stir well. Once heat is turned off, stir in chopped thyme. Serve hot with crusty bread or over rice or polenta.