Antonyms for the word "most flustering" could include words such as comforting, reassuring, soothing, calming, relaxing, and settling. These antonyms represent the opposite feeling of flustering, which is an overwhelming feeling of confusion or frustration. When something is comforting or reassuring, it tends to put one's mind at ease, making them feel calm and relaxed. This is in contrast to the feeling of flustering, which may cause one's heart to race or their thoughts to become jumbled. So, if you are feeling flustered, try to seek out activities or situations that are comforting or reassuring to you to balance out those feelings.