As easy as the title says. All what you need to do is to add an widget at your home screen, press it, write the text-to-speak, accept the call, and that's all. If the text you write is too short, it would be read out fast, so avoid just saying "thanks" by this way.
Then
Call my device
This action will call your device with the IFTTT app installed and speak a message provided by your Applet.
Discover more time saving integrations for VoIP Calls and Note widget