Preheat the oven to 300 degrees. In a medium saucepan, combine the olives with the sour cherries and 1 1/2 cups of the wine. Bring to a boil and simmer over low heat for 5 minutes. Cover and set aside.

In a large enameled cast-iron casserole, heat the olive oil. Add the bacon and cook over moderate heat until the fat has rendered, about 7 minutes. Using a slotted spoon, transfer the bacon to a plate.

Season the lamb all over with salt and pepper. Add the roast to the casserole and brown it well on all sides over moderately high heat, about 8 minutes. Transfer the lamb to the plate with the bacon. Add the beef stock and the remaining red wine to the casserole and bring to a boil, scraping up the browned bits from the bottom.

Return the lamb and the bacon to the casserole. Add the garlic, thyme, carrots, onions, bay leaves, and peppercorns. Cover the casserole and braise the lamb in the oven for about 2 hours and 45 minutes, until very tender and an instant-read thermometer inserted in the center of the roast registers 180 degrees.

Meanwhile, arrange the endives cut side down in a large skillet. Add the sugar, lemon juice, 1 tablespoon of the butter, and 1 1/2 cups of water and bring to a boil. Cover and cook over moderate heat until the endives are tender, about 15 minutes. Uncover and cook over moderate heat until the endives are caramelized on the bottom, about 8 minutes. Season with salt and pepper and keep warm.

In a small bowl, blend the remaining 3 tablespoons of butter with the flour to make a paste.

Transfer the lamb to a carving board and cover loosely with foil. Strain the braising liquid into a medium saucepan and skim off the fat. Boil over high heat until reduced to 4 cups, about 30 minutes. Add the olives, cherries, and red wine and simmer over moderate heat for 3 minutes. Whisk some of the braising liquid into the flour paste until smooth, then whisk the paste into the simmering sauce and cook over low heat, stirring occasionally, until no floury taste remains, about 10 minutes. Season with salt and pepper. Discard the strings and carve the lamb in thick slices. Serve with the sauce and the endives.

The sliced braised lamb can be kept in the sauce and refrigerated overnight. Reheat, covered, in a 350 degrees oven.