message_basic_attachment.json

{
    "channel": "#slackblocks",
    "mrkdwn": true,
    "attachments": [
        {
            "blocks": [
                {
                    "type": "section",
                    "block_id": "block1",
                    "text": {
                        "type": "mrkdwn",
                        "text": "Hello, world!"
                    }
                }
            ],
            "color": "#000000"
        }
    ],
    "text": ""
}