How can I setup a web hook for Slack bot interactions?

I currently have a working dumb bot that cannot interact or respond. I want to use NodeRed for this since they have several node packages that will make interactions easier.

I have tried both the NR chatbot package docs and Getting Started with Ngrok in NodeRed, but I am stuck on the webhook part. When I pass the URL to Slack, it tries to message me back and then NR shows a 401 in the logs.

Is there a better way to do this? The only step in setting up a Slack bot that I need help with is getting the webhook portion for a functioning URL that Slack is happy with.