Once you’re finished with that, it’s time to open PowerPoint’s Slide Master, which is where the rest of the customization will take place. Now, with your blank presentation ready, go ahead and select the slide orientation and size, which you can do by choosing the “Slide Size” option in the “Customize” group of the “Design” tab. You can do so by opening PowerPoint, selecting “New” in the left pane, and then selecting “Blank Presentation” from the template library. To get started, go ahead and open a blank PowerPoint presentation. Creating a custom template in PowerPoint is quite easy.