The phrase "in flash" implies a quick or sudden action. The antonyms of this phrase include slow or gradual actions. Some examples of antonyms for "in flash" are slowly, gradually, systematically, steadily, and methodically. When you take your time to do something, it may turn out better than if you rush it. For instance, when cooking, it is best to add ingredients gradually while waiting for each to cook before adding another. Also, taking gradual steps towards success is more likely to yield long-term success than making sudden decisions. In conclusion, the antonyms of "in flash" show the importance of taking things slow and steady for better results.