Dear Daniel,
Thanks for considering Aspose.Slides.
Master slides are really small and don’t contribute considerably in presentation size.
Anyway, you can get rid of by changing the masters of your newly cloned slides. Aspose.Slides provides Slide.ChangeMaster() method which takes parameter of master slide.
Suppose, you want to change master of slide2 same as that of slide1. Your code will look something like this
Slide slide1Master=presentation.GetSlideById(slide1.MasterId);
slide2.ChangeMaster(slide1Master);
Once, you change the master of all slides to some single master, you can delete all unused Masters using Presentation.DeleteUnusedMasters() method.
Many Thanks and Kind Regards,
Shakeel Faiz
Support Engineer
Aspose Tyumen Team