The word "are slanted" implies a particular angle or direction. Its antonyms are words that describe different angles or directions. Some common antonyms include "are straight," "are level," "are even," and "are upright." These words suggest that something is balanced or aligned properly. Other possible antonyms might include "are perpendicular" or "are diagonal," which suggest specific angles. The choice of antonym depends on context and the intended meaning. For example, "are straight" might be the best antonym when discussing the position of a line, while "are level" might be more appropriate for discussing the placement of a surface.