Step 1: When you open a blank presentation in Google Slides, you should see the Themes sidebar open at the same time. If not, simply select a slide and pick Theme in the toolbar at the top.

How to select a theme in Google slides As of early August 2021, you may apply any of the 23 pre-built, Google-provided slide themes to your presentation in Slides on the web, as well as in the ...

While Google focuses ... on each slide without being distracted by all the visual elements. Another productivity-enhancing feature is the ability to generate a presentation theme from your website.