How to set up and work with Callback correctly?

Question

Flask

Interested in the issue of organizing a callback, for receiving transfers, for example, with the VkCoin Api (yes, they still remember it).
How would it be more correct to organize the server for receiving notifications, and how to configure it, and then how to process the assigned data in the main code. I'm interested in flask, but I didn't find any articles specifically for this task, namely to work with my own vps, and not pythonanywhere and similar nonsense.
I hope for your answer to finally deal with this nightmare for me :)
(I also did not find an answer to my question in the official documentation of flask)