The East Massif provides a backdrop."
As we examined these photos more closely (AS17-134-20511, 20512, and 20513) we noticed, to our utter amazement, that the US flag appeared to have been relocated between pictures.
Then, no doubt as part of an illusion to produce a convincing perspective change consistent with three different camera positions, the mountain backdrop moves even more drastically from shot to shot.
However, the LM stays in virtually the same orientation in all three pictures, as does a row of 10 or so little rocks located between the LM's feet and left of frame. In reality, such a minimal orientation change of the LM would require the distant mountain to change far less than the LM itself - not more.
Moving the backdrops and some foreground detail was all that was necessary to complete the perspective change illusion that went with the different viewpoints. Whistle-blowing photo laboratory technicians would have had ample opportunity to selectively move items around from shot to shot, and if key officials checked the images prior to their release they obviously didn't notice, because the eye sees what the brain wants it to see.
For the rest of this story "How was it done?", see Exposing Apollo