You don't say which version of the program you're using, but version 13 has a completely re-designed slideshow creator.
It is version 12 but that is interesting re: version 13 - I will look into that further. Is there a Whats New feature on Adobe website to show the differences between 12 and 13?
There is on my site, where you can see PDFs describing the new features as well as free tutorials demonstrating them. See the left side of this page.
You asked specially: What is the easiest way to produce a slideshow on a mac?
No Create/Slideshow in Elements Organizer Mac earlier than 13 (current version).. Until program version 13, that Create/Slideshow has been a perk only for Elements Organizer Windows.
But, for 13, the new Elements Organizer 13 slideshow is for both Mac and Windows users. With the new, I have observed that the integration perks in this regard between Organizer slideshow and Premiere Elements Editor are gone - no "Editor with Premiere Elements Editor" output. And, although it offers you a slideshow with 5 possible themes and export as 720p or 1080p AVCHD.mp4 file, you are likely to find the editing opportunities limited. Nonetheless, something to explore.
The easiest way?
Don't over look putting your photos directly into a Premier Elements project through Add Media and putting them on the timeline like a video. There are opportunities for Pan and Zoom, transitions, background music, etc. Premier Elements can even do it with RAW images.
Thanks to you all for your feedback, its been most helpful. I now need to consider if it is worth paying for the upgrade from 12 to 13 especially as I want it installed on both windows PC and Mac.