Link to Slides
When copying and pasting slides from Google Slides into another slides presentation you will be prompted as to if you want to link the slides. This allows you to have a master slide, update information, and have the information updated on the copied slides.
Control C, Control V
To link the slides you must copy from one presentation and paste into the other. In the original presentation click on the slide tile in the filmstrip on the left-hand side. Copy with Control C. (Command C on a Mac).