1. PowerPoint®

1.7. Change Layout

If you select a slide layout and don't like the result, you can manually change the slide layout after you have created the slide.  Right-click on the slide in the left column and choose Layout.

The menu you see when you right-click on the slide also contains options to duplicate or delete the slide. 

It is also possible to create a new slide from this menu as well as from the Toolbar.