How do I change the viewport size between different layouts???

So I'm making a game for mobile, and the main layout will be portrait perspective for the phone. I want another different layout to be in a landscape perspective, so the player will flip the phone 90 degrees when this layout starts. I can't find any way to do this without changing the layout size for all the layouts, so hopefully you can help!

twiltshire

Please don't create duplicate threads with different titles. If you've made a mistake in the title or body of your existing thread, please edit it as opposed to making a new one.

Closing this thread as a duplicate.