From Salesforce logo

The Slack from Salesforce logo emphasizes our position as part of Salesforce, along with other Salesforce brands and systems. Use this logo to build connection to our parent brand and emphasize Salesforce as the owner and endorser of Slack as a product brand. It is also legally required in instances of data sharing.
Paired lockup

In some cases, it may be appropriate to use the Slack and Salesforce logos in tandem. This lockup offers a legible, scalable way to emphasize both brands. Use the paired lockup when cross-promoting or co-presenting the brands. Use this orientation for communication from Slack or on Slack properties. For communication led by Salesforce or a third party, use the Salesforce-first lockup.