Came across this video that may visually show how it's done for those not aware of the procedure. Just freeze the video at 11:30 to see the pipe in the pan that is responsible for the fluid level. Any fluid in the pan that is above that level will flow out if the drain plug is open, and thus adjust itself to the correct level automatically if the temperature is in the correct range. No need to mess with a dipstick that may be hard to read or show a different level on one side. Also, do not remove the drain plug with the engine off as the level will naturally be higher than the pipe, so the fluid will be too low afterwards. Fast forward to 12:20 to see the checking and filling procedure.