Go up to the three dots on the right-hand side of the screen, click on the three dots, and deselect Desktop Site.
This will then cause the slide to go into fullscreen mode. 
At the bottom left-hand corner, you will see the slide numbers. If there is more than one slide, select which slide you want to display on the board.
 
I've also attached a video of a short demonstration. Enjoy!


https://drive.google.com/file/d/1IJ94cQe5QscXEMvnj1cSHCdU0_zQYlIk/view