Consider the case of Quora, which is really SEO-friendly. The problem is that there are no links to questions from Quora homepage. Essentially nothing (even via an indirect URL). So I could never find any link to Quora questions from its homepage; I could only do so via Google (or other search engines), or have a Quora account.
So my question is how to tell Google the list of pages to crawl without listing them all in the homepage (or via an indirect links)?