One of my practices, when I am delivering a workshop, is to be sure I have the link to slide deck on every slide, that way if someone comes in late they can catch up quickly without feeling they need to disrupt the flow of the presentation or any other participants. It works well for presentation in classes as well.
I used to paste the URL on each slide, but inevitably I miss a slide, or have to move it around based on content on the slide already.
Then, I discovered the Master Slide. By changing the master slide I can add the URL (usually a custom one made with bitly) when I make my first slide, then I know it will be there, and can place text and objects on my slides around it.
To access the Master Slide in Google Slides, go to Slide --> Edit Master. Then I add features and make changes as necessary.
Changing the master slides in a deck has many uses...change all headers to the same font/size, change features on only one slide layout, and more.