הרב אליעזר מלמד explains that the way to say tachanun is
על ידי הרכנת הראש והשענתו על זרוע היד
by bowing the head and leaning on the arm.
I understand this to mean that the head is lowered onto the arm.
Is it valid to say tachanun by raising the arm to the head?
The description for tachanun of נפילת אפיים/falling of the face seems to suggest that one should lower the head.