The easiest place to get this is near the end of the game, in the room called "The Crystal Chamber." This is a mostly blue, round room with floating bubbles. You'll do some stuff and eventually use a fiery atomizer on the door on the right - this will take you to a hidden objects minigame.
The trick about this one is that it's in two stages - first, you do the normal thing where you find everything on the list. As you find things, you'll start to see little glowing shapes floating in the air. As you get close to finishing, take a note of the places these are - there will be six in all.
Once you finish the items list, the second stage starts, asking you to find all six of the glowing shapes. If you get all of these in a minute (which should be easy), you'll unlock this achievement.