app.py

assets = Environment(app)
assets.url = '/static'
assets.directory = app.config['ASSETS_DEST']

coffee = Bundle(
    'coffee/models.coffee',
    'coffee/app.coffee',
    filters='coffeescript',
    output='js/app.js'
)
assets.register('coffee_app', coffee)

js = Bundle(
    'js/jquery.js',
    'js/handlebars.js',
    filters='rjsmin',
    output='js/libs.js'
)
assets.register('js_libs', js)

css = Bundle(
    'css/normalize.css',
    'css/main.css',
    filters='cssmin',
    output='css/min.css'
)
assets.register('css_all', css)