Freeze a Geemer on the right of the overhang just below the door to Final Missile Bombway. Freeze a second Geemer on the top left of its platform and setup a moonfall between them. Fall off the Geemers and clip past the floating platform below, past the door shell, and into the transition. This setup is highly precise; if you do not have the right speed you may land on the platform below or the door shell. Falling with too much speed can also cause Samus to go out of bounds.