MySQL slow log deletion while slow-query-log is ON

I'm creating a tool that sets slow-query-log to ON with long_query_time = 0 for 5 minutes to log all queries currently running. The only thing I'm afraid of is that the slow_log will be too big very quickly. From what I see if I delete the slow-query-log file, MySQL doesn't create it back until I run FLUSH SLOW LOGS. The question is: Is it safe to delete it while slow-query-log is on? And do I need to FLUSH SLOW LOGS before doing it? I tried to read the documentation but did not understand how FLUSH SLOW LOGS is relevant and what is its exact purpose.