Google Slides offers a range of options when it comes to selecting a theme for your presentation. There is the option to select a theme from the available selection of pre-created themes which have been designed specifically for Slides. To access the selection of pre-created themes, simply open a new Google Slides presentation, click the “Theme” button in the toolbar, and then choose a theme from the list of options.
In addition to the selection of pre-created themes, you can also upload your own custom theme. To upload your own custom theme, after opening a new presentation, click the “Tools” tab in the toolbar, then select “Upload Theme” from the list of options. Here you can select your own theme, either using a file from your computer, or providing a link to a theme online.
Finally, if you'd like specific theme options, or even a completely custom design, you can work with an experienced designer. Several designers offer their own themes specifically tailored for Google Slides, or you can work with a designer to create a custom theme tailored to your specific needs. Searching online is a great way to find these designers and learn more about the options they offer.