I’m trying to create a view in Interface Builder that contains a UITextView and two UIButtons. In portrait mode I want the view to look like this:

And in landscape mode I want the view to automatically reposition/resize things so that it looks like this:

I’m assuming that some combination of Size & Position, Autosizing, Alignment and Placement properties for the various views and subviews could achieve this, but despite experimenting with a bunch of combinations I can’t even get remotely close to what I’m trying to achieve.
Is this even possible, or should I concentrate on repositioning everything programmatically?
Yes this is possible. Set up your options like this:
TextView: Fixed top, bottom, left and right margins. Flexible width and height
OK button: Fixed left and bottom margins. Fixed width and height
Cancel button: Fixed right and bottom margins. Fixed width and height
Position the views correctly in portrait mode in IB and everything should resize correctly for landscape mode and preserve the layout.
EDIT to show where to find settings.