This is my first time trying my hand at taxidermy of any sort, and I got through the cleaning and bleaching and all that, but because this isn't a full skull (see pictures) and I'm not using a mounting block like would typically be used, I'm not sure how to attach this skull to a plaque properly. Is there any way to screw it on? Or some kind of putty to fill the skull cavity with that could then be screwed into?

Does anyone have some advice? I like the look of the skull, I don't want to dissemble it and use a mounting block.