To send a GIF in Slack, users can type `/gif` followed by a word or phrase they're searching for, hit Enter, and choose from the results. Alternatively, on mobile devices, users can tap the smiley face icon to access the GIFs tab and search for their desired GIF. When using this method, it's essential to be mindful of the content and ensure that the keywords are specific enough to avoid awkward or embarrassing situations. Additionally, there is an art to using GIFs in professional conversations, so users should exercise caution and consider the audience before sending a GIF.