You can create multiple master layouts, and switch between them at any point in a Presentation. If you change any elements in a master layout, all slides based on that master are updated.
Creating a Master Layout
In the View toolbar, click Masters to view and edit master layouts. Click the Add Layout button to create a new master layout. The new master will appear in the outline with a generic name, which you can change by right clicking the master.
To adjust the layout dimensions of your presentation, go to File > Properties > Presentation Properties. Choose the Slide Formats tab and set your desired width and height.
You can now edit the master, adding text, graphics, colors, and formatting. You can delete a master layout by right clicking and choosing Delete.
You may wish to create multiple layouts for introductions, informational slides and conclusions, or simply to vary the look of the content at key points.
Using a Master Layout
After you’ve created a master layout, you can choose to use it when creating a new slide by clicking the dropdown on the Add Slide button.
Changing Master Layouts
If you want to change the master layout that is used for a slide, go to the Slide Properties panel on the right and use the Slide Master dropdown. Choose the desired master layout.