If there is a screen and its unlocked open it and close it on the flyer. If its locked roll the flyer and stick it somewhere on the screen. If there is no screen fold the flyer in half take a corner wedge it in between the door and frame scooting it down. If none of the above works that's when I knock on the door.
Technically it is illigal to tape, wedge, or put the flyer anywhere on the mailbox but most don't care as long as you don't open the mailbox