All levels must be completed with an OCD ranking to earn this achievement. If done in order, it will unlock before you complete the last level of the game
The videos below are examples of how to OCD the levels. They may not be the fastest or easiest ways to get OCD on the levels, but they will give you ideas on how to OCD the level.
The key to this game is patience, so take your time since there is no time limit for most of the levels.
*Note: The videos are not mine.*