I have no idea which version you are using.  You can creeate a project, including theme, plzceholder items, Preferences, master slides in versions before 12 and save them as cptx-project. Lock what you don’t want to be used, and create a new project from that default project by saving it under adifferent name. In Windows you can lock the project file so that the user has to make a copy.

Versions before 12 also have the possibility to save a project as a cptl-file, and there is an option to create a new project from the template file. But that workflow is rather buggy if you hinclude advanced/shared actions and variables.