How to Create a Second Master Slide
PowerPoint gives you the ability to create two or more PowerPoint Slide Masters and then choose which Master you want to use for each slide in your presentation.
To add a new Master to a presentation, follow these steps:
Switch to Slide Master View.
The Slide Master button is found in the Presentation Views group on the Ribbon.
In the Slide Master tab on the Ribbon, click the Insert Slide Master button in the Edit Master group.
A new Slide Master appears. A thumbnail for the new Slide Master is added to the list of thumbnails on the left side of the screen, and the new Slide Master uses PowerPoint’s default settings (white background, black text, and so forth). You can make any formatting changes you want: Change the background color and text styles, add additional background objects, and so on.
Click Close on the Slide Master tab on the Ribbon to return to Normal View.
You can now begin using the new Master that you created.