When submitting a verification ahead of account completion taking a screenshot of the age verification flow will be impossible. Luckily, there is an alternative. When verifying ahead of account creation, use the CTA Templates for 10-DLCs & TF Verifications slide presentation found in the Reseller Google Drive. This slideshow contains a sample age verification flow that can be edited accordingly.
To save an editable version of the presentation, open the link provided > click FILE > then click either MAKE A COPY or click DOWNLOAD to save the presentation as PPT. Then, edit the age-verification slide as needed and save a screenshot that can be used with the verification.