The phrase "seeing how flies" is an idiom that means to pass time idly or to do something without a clear purpose or goal. There are several different synonyms that can be used to convey a similar meaning, including "killing time," "wasting time," "frittering away" or "idling away." Other similar expressions might include "whiling away" or "passing the time," which suggest a casual and unhurried activity. Regardless of the specific wording, the idea is that the activity being undertaken is not particularly meaningful or productive but is simply being done to pass time in a leisurely manner.