In a recurring series, Vanity Fair pulls back the curtain on awards season’s most visually enticing films, revealing exclusive details of the creative process of art directors, costume designers, makeup artists, cinematographers, and more. This week, three-time Oscar winner and production designer Stuart Craig explains how he turned a roll of paper, some dollhouse furniture, and a set of paints into Gringotts, Diagon Alley, and the Room of Requirement—among many other Harry Potter locales…