The Multiple Ways criteria states that you must be able to access a webpage from all other site-pages in more than one way. For example, a main navigation alone is not acceptable.
This criteria allows users to access information more quickly and efficiently if browsing the site through a screen reader or magnifier.
If your webpage is, "the result of, or a step in, a process," this rule does not apply. An example of this would be a thank you page, like the below. Because this page occurs as a result of submitting a form, it does not need to be widely accessibly by navigation or sitemap.
Another practical example would be the WCAG Recommendations navigation on the right sidebar of this site page. The WCAG articles are accessible through this menu, the search menu and the top-level WCAG page, so this passes the criteria.
On the manual intervention side, the inclusion of a footer navigation, sitemap, or search function all meet the Multiple Ways standard.