Flutter: How to show AppBar only after scrolling?

That's what you read. I don't want to hide AppBar when scrolling, there's a lot of info on that.

What I want is the exact opposite. I want my homepage to open with no AppBar and then, when the user starts scrolling, the appbar will be displayed.

This website does exactly what I want to reproduce: https://www.kirschnerbrasil.cc/ (in the desktop version).

I guess I need do use the SliverAppBar, but I haven't manage to do so yet. Can anyone help?

Thanks!