For my 1920's ensemble that I wore to the 2015 Art Deco Preservation Ball, one of the things that made it authentic were my undergarments.  I really wanted the silhouette to look period-correct, so i found a pattern for a 1920's corset.  The corset really gave me that "Cylinder" shape that was au courent during that part of the early 20th century.  The look was topped off with knickers made from a real French pattern made in the period and seamed stockings from What Katie Did.