Serving static HTML with Vaadin and Spring Boot

I’d like to create a Spring Boot web application using Vaadin. My goal is to have some unprotected “welcome” pages serving static content, e.g.

And then have a protected/functional web app using Vaadin under a context like “/app/” e.g.

I’ve looked around for tutorials on serving HTML in Vaadin but I’m having a hard time identifying which approach I should take. I’ve seen a lot of references to Polymer templates, the /src/main/resources directory, the /frontend/ directory, the /VAADIN/ directory, etc. Can anyone recommend an approach or a tutorial I should follow? I am running Vaadin 14.1.20