Heat the oil in a large skillet over high heat and brown the roast on all sides.
Place the carrots, onions, celery, bay leaves, and pickles in the slow cooker.
Place the roast on the vegetables.
In a small bowl mix together the wine, mustard, cloves, salt, and pepper, and pour over the meat.
Cook covered on high heat for 4 to 5 hours, or on low heat for 8 to 10 hours.
Prior to serving, remove the meat and vegetables to a warm platter with a slotted spoon.
To make the gravy, pour the remaining liquid into a small saucepan and skim off and discard the fat.
Stir in the cornstarch mixture and bring to a boil over moderate heat, stirring constantly.