The phrase "making the top of one's head" typically refers to a process of coming up with an idea quickly, without much thought or planning. Antonyms for this phrase would be terms that convey a more deliberate, thoughtful approach to problem-solving. Words such as "analyzing," "deliberating," "reflecting," and "pondering" all suggest a more careful, considered approach to generating ideas or solutions. Other antonyms might include "slowing down," "taking time," "working methodically," or "approaching thoughtfully." These words all suggest a conscious effort to avoid hasty, impulsive decision-making, and instead focus on developing more thoughtful, reasoned approaches to problem solving.