1-hour free play casinos were a popular thing back in the early 2000s when most of the available online casinos were downloadable and managed by Microgaming. Today, it's pretty much impossible to find such offers that would allow you to play online slots free for the first hour.
This doesn't mean you can't do so, though! Many of our online casinos offer a free sign-up bonus you can claim without making a deposit ad play for free. Check out our list of free play casinos.