We can statically bootstrap an application by taking the plain ES5 Javascript output of the generated factory classes. Then we can use that output to bootstrap the application:
import { platformBrowser } from '@angular/platform-browser';
import { AppModuleNgFactory } from './main.ngfactory';
// Launch with the app module factory.
platformBrowser().bootstrapModuleFactory(AppModuleNgFactory);
This will cause the application bundle to be much smaller, because all the template compilation was already done in a build step, using either ngc or calling its internals directly.