It works fine. I have many Stringify flows that are initiated by voice command into IFTTT. Go into IFTTT and create an applet. Use GA as the "this" rigger and set whatever phrase you want (you can set 3). Set what you want GA to reply if you want. Then as the "that", select Stringify and choose the flow you want to execute. Of course, before this you will need to have created a flow in Stringify with the IFTTT Thing in it. It works a dream.
Alternatively, use the approach Kris mentions above. Set up a shortcut in GH. You set a voice command phrase for GA and tell it what you want to execute. In this case you type the command "tell stringify run la la la". It also works fine.