portrait orientation powerpoint

I have downloaded PowerPoint from Apple Store and have a Microsoft 365 subscription (personal).

Trying to create a slide on PowerPoint and want it in portrait orientation.

Can’t seem to do that. I have tried going to design -> slide size but I only get options of Standard and Widescreen - no custom sizes or page orientation information.

Is it possible to create a portrait orientation slide on PowerPoint Ipad?

If so, how?

If not, why is that? Seems like a very basic feature that should be included.