For this thing, I downloaded just one app, Deck. Two of the four suggested apps were for iPad only, and I never bring my iPad to work. The other, Haiku Deck, required that an account be created. Since I don't expect to keep a presentation app on my phone once 23 Mobile Things is over, I opted not to create an account I'd never use.
Although quite basic, Deck was fairly intuitive. I created a new slideshow of about 6-7 slides. I added some text, added a photo/caption. I didn't really play around with themes very much, but some of them were quite visually appealing. If I had a reason to create a simple slideshow on the fly, and I can't actually think of one, this wouldn't be a bad choice.