Set Default Layout Add-in for PowerPoint 2000 or later

PowerPoint always creates a new presentation with a slide with the Title layout. There no way to set a default layout to be used whenever a new slide is inserted into the presentation. The Set Default Layout add-in is specifically designed to tackle this annoyance. Load the add-in and select the default slide layout, from this list.

Click here to download

Instructions:

Download and unzip the contents to a folder.
Launch PowerPoint and load the add-in 'Layout.ppa' (To learn how to load an add-in click here).
A 'Defaults' combo box will appear on the 'Standard' menu bar.
Select the layout in which the new slides should be inserted.

Now whenever you insert a new slide it will apply the layout selected in the combo box automatically.