please attach sample of ppt how it needs to generate as i am not clear if a empty slide needs to withing the <page> loop or outside the page loop.
regardless of the solution you either apply page tag on all 3 slides using method which is described on official help page or you create 2 page tags and apply them separately on each of the slides
also as you are asking quite a lot of basic questions I suggest that you always start by checking first the help.qlik.com for solutions as it covers 99% of the functionalities and is always up to date with the version you are using (functionalities vary a lot between versions).
cheers Lech, When applicable please mark the correct/appropriate replies as "solution" (you can mark up to 3 "solutions". Please LIKE threads if the provided solution is helpful to the problem.