I love to use collaborative Google Slides. I am frequently asked about how to keep students from editing my slides in the template. While you can not restrict editing on Slides like you can a Google Sheets spreadsheet, there is a trick that will help keep the slide from being edited.
Create the Slide
First, create the slide with the images and text that you wish.
Download as PNG
Delete the Slide
Delete the slide. The current slide has the ability to move the text and images around.
Insert Blank Slide
From the layout options, insert a blank slide.
From the toolbar, choose the “Background” button.
Choose the Image and upload the image of the slide you downloaded. This will set the slide content as the background image, which can not be easily manipulated by students.