I just needed an excuse to play around with the Slack SDK for Python, AWS Lambda, APIGateway & Comprehend, and the Serverless framework.
Much thanks to the karmabot-tutorial person here, which got me started a lot quicker than if I had to come up with everything from scratch! https://www.sentialabs.io/2018/08/16/Building-a-Slackbot-with-Serverless-Framework.html