If you create a Google Slides template and want to share it with others you can modify the end of the Slides URL to turn your slides into a template.
Change the Sharing Permissions
By default the sharing permissions on any file is private. You can not share templates of private files. Make sure you change the sharing settings to anyone with the link can view.
Modify the URL
For this “Critique the reasoning of others” template the URL is
Edit the end of the URL where it starts with slash edit to /template/preview instead.
Share this modified link to force a template preview where the user can click on “Use Template” in the upper right hand corner.
This feedback template is not much to look at, the preview is white, but click on the tiny triangle next to the add a slide icon in the toolbar to see the layout template. This allows you to add feedback slides to student work if you use this as the Slides you attach into Google Classroom for student copies.