gem install heroku
heroku login
heroku keys:add
git clone git@github.com:sethvincent/sinatra-skeleton-heroku-static-pages-example.git
git add .
git commit -m 'stuff'
heroku create
heroku create --stack cedar
git push heroku master
That should be all it takes to use sinatra on heroku to serve static files.
This example includes the skeleton css framework in the public folder to help you out if you're starting from scratch.