GoodAdvertisements Inc works with several companies to support global advertising campaigns and are on a paid plan. They are preparing for a campaign launch that requires input from multiple companies.
GoodAdvertisements Inc wants the ability to coordinate effectively with the companies before and during their respective launch in a private channel, but it is not clear whether the companies use paid Slack plans. The Admins at the company want to take security precautions before inviting any outside individuals into their Slack workspace.
What is the best way for the Admins to have the individuals from the outside companies join the Slack workspace and ensure the process scales for future launches with other companies?