The antonyms for the word "makes flat" are words that indicate the opposite action, which is to make something uneven, bumpy, or wrinkled. Some of the antonyms of "makes flat" are words like roughens, crumples, wrinkles, rumples, creases, corrugates, ruffles, rummages, tousles, and puckers. These words are often used to describe the opposite of what smooth and flat surfaces might represent, such as the rugged terrain of a mountain, the wrinkles on an old person's face, or the tousled hair of a child who has just woken up. In short, the antonyms of "makes flat" describe the opposite of smooth and flat surfaces.