Congratulations! That’s the same method that we use in the wiki FAQ.
Note that the present time you must use A virtual device which is both a virtual switch and a virtual contact sensor, because echo will only let you create routines that trigger off of sensors or the echo button, not other switches. So your step eight doesn’t describe what people actually see in the app. Instead at that point they will be selecting a sensor to open, not a switch to turn on.