Wipe roast with a damp cloth. Combine salt, pepper and flour. Rub the roast well. Place in an open pan. Bake at 300~ for 2-1/2 hours. Cut green peppers in halves. Remove centers and seeds. Parboil until slightly tender. Drain. Mix together rice, celery, and chili sauce. Fill peppers. Place around roast. Bake at 300~ for 40 minutes or until peppers are tender and roast is done.