I am also completely flat footed (wet footprint has no arch) and I was using a standing desk for 6 months with no issues. I wore running shoes, stood on a thin

I am also completely flat footed (wet footprint has no arch) and I was using a standing desk for 6 months with no issues. I wore running shoes, stood on a thin pad (the floor is hard tile), and took sitting breaks in a bar stool about 3 times a day for 20 minutes. I also had a bar about 15 inches off the ground for me to put a foot up on (this is a must as far I'm concerned). Basically if you are wearing shoes you can walk/run in, they should be good enough for standing.