Voice experiences should be designed, before starting any development. These days, it is easy to develop with the tools and templates available for Amazon’s Alexa and Google’s Assistant. So easy, even a kid can do it (tried and tested on an 8 year old!)
I wrote about the approach for Designing Voice Experiences for Smashing Magazine, with the companion UX Quiz Skill for Alexa.
Used this at clients including Discount Tire.