
Hi Imran,
the recommended way to patch a large SharePoint Server 2019 farm is using the zero downtime patching method in combination with side by side functionality which allows to patch SharePoint without a maintenance window.
You can find relevant details in the following articles:
https://blog.stefan-gossner.com/2016/04/29/sharepoint-2016-zero-downtime-patching-demystified/
Ensure to also review the SharePoint server patching best practices article:
https://blog.stefan-gossner.com/2020/02/11/sharepoint-patching-best-practices/
Cheers,
Stefan