Hi Suresh P,
Thanks for inquiring Aspose.Slides.
I have observed your requirements and regret to share that Aspose.Slides for .NET does not offer the facility to create the layout slides from scratch. In fact the default layout slides that are generated when creating any presentation using PowerPoint are in fact added by Aspose.Slides when instantiating PresentationEx instance. However, Aspose.Slides fully allows you to access the layout slides inside presentation and can alter them to meet your needs by adding new shapes or modifying/deleting existing ones. For reference, please visit this thread link where by I have assessed different layout slides and every shape inside layout slide and copied them to empty normal slides. The relevant part for your convenience in the shared sample code is how to access different layout slide and access shapes inside them.
Also, you can apply any layout on slide out of layout collection. The best approach will be to create the template layout in PowerPoint and access that using Aspose.Slides and apply them on slides using Aspose.Slides.
I have unfortunately not been able to understand your second requirement. Can you please share some more information in this regard and possibly in the form of snapshot. I will try to help you further in this regard.