Cut steak horizontally from a long side to within 1/2 in. of opposite side. Open steak so it lies flat; cover with plastic wrap. Flatten to 1/4-in. thickness. Remove plastic; sprinkle steak with 1/8 teaspoon salt and pepper. Set aside. In a skillet, cook bacon until crisp. Remove to paper towels. Drain, reserving 2 tablespoons drippings., In the drippings, saute leeks, yellow peppers and 1 cup celery until tender. Stir in spinach, thyme, basil and bacon. Spoon over meat to within 1/2 in. of edges. Roll up tightly jelly-roll style, starting with a long side. Tie with kitchen string., Rub steak with garlic and remaining salt. In a large skillet, brown meat in oil on all sides. Place in a greased shallow roasting pan. Add onion and remaining celery. Combine remaining ingredients; pour over steak. Cover loosely with foil., Bake at 350° for 1 hour. Baste with drippings. Bake, uncovered, 15 minutes longer or until meat is tender. Let stand for 10-15 minutes. Remove string and slice. Discard bay leaf; thicken juices if desired.