You can definitely do this, but there’s a trick to it. Echo routines can only be triggered from a sensor, not a switch. But you can create a virtual device in smartthings which is both a switch and a sensor. This allows you to turn it on and off like a switch, but Alexa will see it as A sensor opening and closing and you can trigger the routine off of that.
Complete instructions are in the community FAQ. This is a very popular use case. 