Create a Slack app (here).
Assign a name and a workspace in the following steps.
After setting up the Slack app you have to add features like the slash command, interactive components and permissions.
Start with creating a bot user named erna.
Continue with the slash command, extend the root url of the future service with /commands and other options like the command name and a hint.
Continue with the interactive components which enables to ask for the current location.
Extend the root url with the /actions path.
Finally grant the required permissions
users:readchat:write:botmpim:writeim:writecommandsbot
and install the app to workspace.
Note the provided Bot User OAuth Access Token to deploy erna.
