Section 8 of the OGL is the section that requires you to identify Open Game Content. What you seem to be talking about here is the language you'd use to make that declaration.
Strictly speaking, that declaration doesn't have a standardized presentation, but there are many examples of it (and the declaration of Product Identity) that you can copy-and-paste into your own book. For instance, here's something from a recent product I bought:
(Obviously, you'd replace the parts that say [company name] with whatever company name you're publishing under.)