You want prospective users to be able to install your app directly from the Slack...

Slack's Direct Install URL is specifically intended to eliminate the extra step of routing prospective installers through the application's own landing page before starting OAuth. Current Slack Marketplace documentation states that when Slack sends an HTTP GET request to the configured Direct Install URL, that endpoint must respond with an HTTP 302 redirect to a fully qualified Slack OAuth authorization URL. For modern Slack applications, the redirect target follows the OAuth v2 authorization pattern: https://slack.com/oauth/v2/authorize. The URL includes the application's client ID and appropriate OAuth scope information. Slack then presents the authorization interface to the installing user. After consent, the normal OAuth authorization-code process continues through the application's configured redirect URI. Option B represents the conventional landing-page installation flow that Direct Install exists specifically to bypass. Option C confuses installation behavior with Slack's three-second acknowledgment requirement for interactive requests and Events API deliveries. A slack:// deep link is not the required Direct Install target. Therefore, D is precisely supported by current Slack Marketplace documentation. The question's older phrase Slack App Directory should now be read as Slack Marketplace. This maps directly to Distribute Your App.