Valley fold the corner at a 45 degree angle. Unfold to Step 3. Valley fold the edge perpendicular to the rest of the paper. Collapse the model, keeping the extra paper locked away, as shown in diagram 12. Lock the edge by valley folding through all hidden layers.
Valley fold the white edge in, and tuck into the pocket.
Valley fold at a 45 degree angle. Mountain fold the frame in half. Mountain fold the frame in half again. Valley fold the frame. Each side should be slightly longer than the corresponding side of the door.