Google Slides, which is an amazing free resource, from Google....
Slides Carnival, you can add several more to your bank of beautiful designs to use.
Take a look at a few of the awesome presentation templates they have created....
You go to the presentation template that you want to use and click on the orange button at the bottom. It says Use This Presentation Template.
You will find the directions here.
It is that simple.
If you have questions on how to use Slides Carnival or any others, they have a great place to go on their website that gives this information and tells more about the designer of the templates.
Such a fun company....and such a fun place to go when bringing lots of life and beauty to your presentations! And of course....share this with your students and others too.