Make just one slide different size in Powerpoint
powerpoint
Solution
You can't. You can only have one slide size and one orientation per presentation.
Are you projecting the presentation or delivering it on a laptop? If so, the size is sort of irrelevant. Regardless of the slide size, the projected/displayed image will never be longer or wider than the projector/display accepts.
Problem
Making a powerpoint that's supposed to show a before and after of a website. Since it's currently a long website I'd rather make a single long slide to put it on (20" instead of 7.5"). But all the other slides in the presentation should be normal-sized. I found Slide Size (Design ribbon, Customize section) but that resizes ALL slides.