Heat the oil in a large heavy saucepan over medium high heat. Add the ham hock, onions, celery, and bell pepper and cook, stirring, until the vegetables are soft, 4 to 5 minutes. Add the bay leaves, thyme, and garlic, and cook, stirring, for 2 minutes. Add the beans and chicken stock and bring to a boil. Reduce the heat so that the beans just simmer and cook, uncovered and stirring occasionally, until the skin on the beans is tender and the beans begin to soften, about 2 hours. Season, to taste, with salt and pepper. Add the sausage and continue to cook, stirring occasionally, until the beans are soft and creamy, about 1 hour longer*. (If desired, the ham hock can be removed at this point and either discarded or, when cool enough to handle, the meat can be removed from the bone and returned to the beans and the bone and skin discarded.) Remove the bay leaves and thyme sprigs and serve the beans and sausage over hot white rice.
Pass the hot sauce at the table for guests to use at their own discretion.
*The cooking time for dried beans can vary greatly depending on the type of bean as well as the freshness. Salt should not be added until after the skins on the beans soften.