To make changes to the slide master or slide layouts, on the Slide Master tab, do any of the following: Associated slide layouts are positioned beneath the slide master. The slide master is the largest slide image at the top of the slide thumbnail list, to the left of your slides. On the View tab, in the Master Views group, choose Slide Master. On the Design tab, select Slide Size > Custom Slide Size and choose the page orientation and dimensions you want. Open a blank presentation: File > New > Blank Presentation
