JUST FOLLOW THESE SIMPLE INSTRUCTIONS:
 Declare your intention to create a 'composition.'
 Start a piece at some time.
 Cause something to happen over a period of time (it doesn't matter what happens in your 'time hole' -- we have critics to tell us whether it's any good or not, so we won't worry about that part).
 End the piece at some time (or keep it going, telling the audience it is a 'work in progress').
 Get a part-time job so you can continue to do stuff like this.
The Real Frank Zappa Book, 1989 (PDF aqui)