Undocked gauges in MSFS
is really easy using the MSFS Pop Out Panel Manager.
It pops out all undockable panels you wish by just one click after setting it up. But not only that... It also places them where you like and removes the MSFS title bars.
Running those (undocked) gauges on my instrument monitor brought the annoying effect to have the backlight of the screen shining through the gaps between the gauge panels.
To get rid of it, i designed a set of 3d Printed frames i could easily clip together - without the need of glueing them and place them just in front of the screen.
As my monitors are mounted behind a 12mm wooden board, there is a space where i can easily put them in without any need for 'mounting' them. If i change the aircraft, i just replace the gauge frame and undock again the gauges with the panel manager. That's it!