1. For reference, the timers will be called biggest timer, midsize timer, and smallest timer.
To open the door, you have to make the timers all land in the green zone at the same time.
Starting with the biggest timer, when the biggest timer hand is facing straight down, start the smallest timer. When the biggest timer hand is facing straight left, start the midsize timer (After you hit the smallest timer you pretty much immediately hit the midsize timer)
Keep trying if you don't get it the first time.
Hit like if this helped you!
2. Proceed to the next floor!