Using Slack SCIM API to provision users via SailPoint IIQ

I want to use SailPoint IIQ to provision and de-provision Slack users via Slack SCIM API. Slack SCIM API uses version 1.1. and uses Basic or OAuth for authentication. I have setup a Slack Enterprise account, generated the API key, and the SCIM API call works via Postman or cURL. However, I am unable to setup the Basic Auth or OAuth tokens for authentication. Please help!