A Slack app initially created for one development workspace cannot simply be installed into unrelated workspaces. To support multi-workspace installation, the application must implement the Slack OAuth authorization flow and enable distribution. A key prerequisite is configuring an OAuth Redirect URL. After an installing user authorizes the requested scopes, Slack returns a temporary authorization code to this redirect URI. The application's server then exchanges that code using oauth.v2.access for installation credentials. Slack's official distribution documentation also requires the developer to enable application distribution from the app-management interface. Historically the setting is described as Activate Public Distribution; current documentation may refer more generally to app distribution or unlisted distribution. Marketplace publication is not required merely to make an application installable by other workspaces. An unlisted distributed application can be shared directly with selected customers through its installation flow. Option C contains a serious security defect because workspace and user IDs must not be hard-coded. Option D does not establish multi-workspace authorization. Therefore, A provides the minimum architecture required for cross-workspace installation. This maps directly to Distribute Your App, particularly OAuth, redirect URLs, and distributed installations.