Under Orientation, select the orientation you want. To set the page orientation for all of the slides in your presentation, on the Slide Master tab, select Slide Size > Custom Slide Size. To apply a design or theme-based colors, fonts, effects and backgrounds, see Create your own theme in PowerPoint. To remove any of the built-in slide layouts that accompany the default slide master, in the slide thumbnail pane, click each slide layout that you want to delete, and then on the Slide Master tab, click Delete. To create one or more custom layouts or to modify existing layouts, see Apply or change a slide layout. Note: In the slide thumbnail pane, the slide master is the larger slide image at the top, and the associated layouts are positioned below the slide master.
