Load up the Turtle puzzle from the easy difficulty.
You can either beat it legit or spam hints by pressing the "H" key on your keyboard or clicking on hint in the drop down menu on the upper left corner. Two tiles will glow once you activate a hint. Click on either of them to clear the set from the board. Repeat this until the puzzle is completed. You may need to do a reshuffle and/or undo if you run out of moves, which is very unlikely on an easy puzzle using hints.
Now repeat this 19 more times to finish off this achievement.
If you use the hint method then this should take you well under a minute per puzzle.
As per Noah Wetjen...
For any Germans wondering: Even though the German description of this achievement says that you need to complete the same puzzle 3 times, you still need to do it 20 times like it says in the English description. Just a very weird translation error.