1. Click on the settings button on the top right corner of the Google site and a drop down menu will appear
2. Click on "Manage Site"
3. Then click on "Themes, Colors, and Fonts" which is found on the left side of the page
4. Change the Base theme found on the top of the page to "Blank Slate" as shown below.
5. Then click on the red "Save" button to save all changes