I continued the guide today. I created an IAM User for zappa-deploy on AWS, configured the credentials locally, deployed the Skill with Zappa, and configured the skill in the Alexa developer console.
Testing the skill showed an error though,
There was a problem with the requested skill's response. I replaced my Python
code with a simple one-line response in case the problem is version
incompatibility, but I still received the same error. This is really strange
because I followed the guide pretty well; the only exception is that I’m using
Python 3 (flask-ask and Zappa currently support it).