In June, Apple updated the App Store Review Guideline 5.1.1, section (v), stating that all apps that allow for account creation must also allow users to initiate deletion of their account from within the app. This requirement applies to all app submissions starting January 31, 2022.
If you already have a deletion workflow on your website or you just created one, you just need to integrate that flow into your application. You can do that by adding the URL of your existing page from your website, where you initiate the deletion of the users' account, as an iframe page inside the application, as shown here.
If you don't have a deletion workflow on your website you need to create one before following the instructions above.
After that, you can also link the newly created page from your application to any other page you want, for example, your settings page, as shown here.