Using a large colander, rinse the dried beans under cold water, sorting out any debris. Transfer to a large bowl and add enough cold water to cover by a few inches. Allow the beans to soak overnight. Then drain and set them aside.
Place a large Dutch oven over medium heat and add the olive oil. When the oil is hot, add the sausage and stir frequently to brown, about 5 to 10 minutes. Remove the browned sausage from the pot, leaving the oil behind, and set it aside.
Add the onions and celery to the hot oil remaining in the pot. Cook, stirring occasionally, about 10 minutes or until the vegetables are softened.
Add the garlic, bay leaves, dried thyme, pepper, and 1 teaspoon of the salt. Cook the mixture, stirring frequently, for about a minute or until the garlic is fragrant.
Return the browned sausage to the pot and add the presoaked beans and the chicken stock.
Bring the mixture to a boil. Then adjust the heat down to a gentle simmer and cook uncovered for about 45 minutes, or until the beans are only slightly firm.
Add the rice and the remaining ½ teaspoon of salt. Give the mixture a good stir. Then cover with a tight fitting lid and cook for another 15 to 20 minutes.
Remove the pot from the heat and let the mixture rest, still covered, for about 10 minutes. When the rice has fully plumped and finished cooking, the dish is done.
Serve either hot or warm, discarding the bay leaves. Garnish with a generous sprinkling of chopped scallions over the top.