How to Make It
Preheat the oven to 350° Season the pork roast lightly with salt and generously with pepper, rubbing the seasonings into the meat. In an enameled cast-iron casserole just large enough to hold the roast, heat the oil until shimmering. Add the roast and cook over moderate heat until well browned all over. Transfer the roast to a large plate.
Add the salt pork to the casserole and cook over low heat until softened but not browned. Add the onions, garlic, carrots and celery and cook over moderate heat, stirring occasionally, until the vegetables are very tender, about 20 minutes. Add the wine, bay leaves, sage and thyme and bring to a boil. Remove from the heat.
Carefully set the roast, fat side up, in the casserole. Cover and bake in the oven for 30 minutes. Turn the roast, and if there is very little liquid left in the pan, add 1/2 cup of water or more to keep the vegetables moistened. Bake for about 20 minutes longer, or until an instant-read thermometer inserted in the center of the roast registers 150°.
Transfer the roast to a carving board, discard the strings and cover loosely with foil. If the pan juices are thin, boil them over high heat until thickened. Season with salt and pepper. Slice the roast and serve with the vegetables.