Rotation and sizing in app development

Say you want an app to be for both iPad and iPhone and have different screen layouts in portrait vs landscape for each. I remember seeing somewhere on the devnet a video on how to do this...you actually created 4 different files, one for iPad landscape and one for iPad portrait etc. And the you linked them to a single ipa and it auto discovered which device was being used and auto rotated the screen...but I can't find that information anywhere again! I've google and looked all over devnet but now I'm wondering if I made it up. 😕😕

How does one go about doing this? Is there a video or resource on devnet somewhere?

Thanks!