Because one of the main accent error patterns on word endings is devoicing (saying a voiceless sound rather than a voiced sound), we looked at voiced and voiceless sounds. Read more about this and practice here.
We looked specifically at practicing final z, the errors, and the steps to work on changing these errors. You can view more videos and see practice materials for final z here.
More practice for z: american-accent-error-patterns-s-for-z.html
You can also work on these patterns and all of your accent patterns in my online courses. Get a free trial here.