Without seeing the handbook or knowing its contents, it will be hard for anyone to offer up some meaningful insight to what needs to be in the slide show. I would progress in the following manner. Assuming you have read over the employee handbook, I would highlight what you think would be three or four main or pertinent ideas from the document. I would then devote about three to four slides on each topic identifying the reason for its inclusion in the handbook, what its basic function is, how it is meant to protect and serve both management and its employees, and how it will be enforced or consequences for not following it. I would then add a slide at the end encouraging the audience to read the handbook for themselves as the slide show only represents some basic ideas or the important points from this document that governs the relationship between management and its workers. A title slide at the front should be able to get you your 10 to 15 minimum. Finally, remember to condense your points and ideas to "bullets" or "talking points" as opposed to writing out paragraphs on slides.