Creating a presentation in Keynote
My designer usually does my decks in in-design at 17 x 11. What's the custom size if I want to work in Keynote?
MacBook Pro 15″, macOS 14.5
I'm not sure I understand the question...
If your designer is creating decks at 17 x 11 (presumably inches?), then set your presentation to use that - use the Document tab -> Slide Size -> Custom Slide Size and enter the size that you want (noting that Keynote wants points vs inches for its measurements). The slides will automatically scale to fit your presentation screen when you present.