A canonical redirect is the quickest solution to address duplicate content issues caused by trailing slashes. If you choose to implement the 301 redirect, both users and search engine crawlers will always be sent to to one of two URL versions: with or without slashes.
If you do not know how to code, Permalink Manager may help you in using the redirect. To make it work and force your chosen slashes configuration, enable the "Trailing slashes redirect" option in the plugin settings.