1 Solution
In order to view and grade your students' assignment submissions, you will be using the "Grades" feature along with the Gradebook. Once you enter the Gradebook, you will select that individual assignment. After you enter that assignment, you will be able to view your students' submissions and assign them each a grade. Now, just make sure they also gave you viewing access of their Google slides. 
How do I view assignments or students individually in the Gradebook?
How do I download all student submissions for an assignment in the Gradebook?
Here's more information about Grades in Canvas:
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.