There are 6 opportunities to do this trophy - 3 Roxxon Labs and 3 Underground Hideouts. Completing any of these without detection will result in the trophy. This is easier the higher level that you get, as you can put skill points into the camouflage skill tree. You can also complete the stealth trainings to boost your stealth/camouflage as well.
Clicking the left joystick (L3) while in a base will highlight the enemies. It will also tell you if it is safe to grab the enemy you are focused on. Perch and wall takedowns are easiest as you stay up above the enemies. Also, take downs with the remote mines count as well. Using these techniques and the camouflage take downs when you can, this should be relatively easy to get.
If you are seen, you can always retry the mission from the start screen or the map so this should not be a missable trophy. Good luck!