Create a new Bot Integration under services/new/bot.
On the next screen, note the API token.
Set SLACK_API_TOKEN from the Bot integration settings on Slack.
heroku config:add SLACK_API_TOKEN=...
AWS key and secret.
AWS region to connect to, eg. us-east-1
.
SlackAws replies with animated GIFs. While it's currently not necessary, you may need to set GIPHY_API_KEY in the future, see github.com/Giphy/GiphyAPI for details.
Heroku free tier applications will idle. Either pay 7$ a month for the hobby dyno or use UptimeRobot or similar to prevent your instance from sleeping or pay for a production dyno.