How to use the Gallery block to create an image slideshow.
Simple Gallery, Default Settings
The Gallery block shows a set of image thumbnails. By default, the thumbnails are displayed, in the chosen layout, with no click-through effect.
Gallery with Click to Full Size
Edit the gallery block. In the Block Controls toolbar (above the block) choose “Link images to media files” to allow clicking through to larger size versions of each image. You can also choose “Open images in a new tab“, in the sidebar settings, which allows the visitor to stay on the original page while opening and viewing the larger images.
Gallery with Lightbox Effect
Edit the gallery block and choose “Enlarge on click” from the Block Controls toolbar to display the full-size images with a lightbox effect.
Gallery Slideshow
A gallery with the “Enlarge on click” lightbox effect behaves as a simple slideshow by default, by enabling visitors to click on arrows at the sides to traverse through the images, or to swipe through on mobile.
It might be useful to investigate how to animate the transitions differently.
For a more sophisticated slideshow effect, with interesting transitions, or including content other than images, a slider plugin, such as Smart Slider 3, or Carousel Slider Block, is needed.
But this simple “traverse to the next image” effect is a very good addition to make viewing a gallery a more user-friendly experience.