Just to add to the consensus... Trying to see the sides of my head when shaving is tough (not being a flounder myself - though I guess a flounder has a REALLY tough time seeing the "other" side of it's face...) :rofl2: but I digress...
The solution was to swap sides with my wife and move my shaving area next to the medicine cabinet on the side of the sink area. That gives me a giant mirror in front of the sink and the medicine cabinet mirror to the side which I can open partway to see the sides of my head/face. Barring the ability to use a cabinet mirror, Tarkus has the right idea! Tom's comment about makeup gave me an idea too - seems one could use that magnifying mirror to trim ear and nose hairs between barber visits too.