Post Incoming Webhook messages

You can use SlackApiClient.chat.postWebhookMessage() to post Slack Incoming Webhook messages:

client.chat
    .postWebhookMessage(
        url = "https://hooks.slack.com/services/...", 
        req = SlackApiPostWebHookRequest(
          text = template.renderPlainText(),
          blocks = template.renderBlocks()
        )
     )

This method available to use without API tokens. The Webhook URL could be gather either from OAuth responses or from your Slack app profile configuration.