A slip dress for black tie is the definition of letting the occasion speak for itself through simplicity. This is a bare bones silhouette. Usually knee length or midi, often sleeveless, the construction is minimal and the fabric does all the talking. Silk or silk blends drape differently than cotton and the drape is the point. A slip dress works because the fit needs to be correct and the fabric needs to be quality enough to not look cheap. You can wear it alone or layer it. The color is usually black or deep jewel tone. These slip dresses prove that black tie dressing does not require decoration when the silhouette and fabric are right.