The antonyms of the phrase "more hastily" could be numerous depending on the context. Here are some commonly used antonyms for this phrase - slowly, leisurely, calmly, methodically, systematically, deliberately, gradually, cautiously. In most cases, when we say someone is doing something hastily, we mean that they are doing it quickly without paying enough attention or care. The antonyms for this trait can vary depending on the situation. For instance, if we are talking about cooking, the antonym for more hastily would be slowly or methodically, but if we are talking about escaping a burning building, then the antonym for more hastily would be cautiously or gradually.