Can I use Slack’s block kit?

Hello, I have a configuration question. I’m trying to format a payload to deliver a slack message using the Webhook JSON carrier. I’m able to get a very simple message through successfully, but when I try to use slack’s block kit, nothing comes through. For testing purposes, I’m able to use the block kit json successfully through other means, but when applied in this plugin, it fails.

I have the setting “Remove unused merge tags from sent values” unchecked.

Example of what works:

{
    "text": "*{post_title}* was just published.  Check it out here: {post_permalink}"

}

Example of what doesn’t work:

{
	"blocks": [
		{
			"type": "section",
			"text": {
				"type": "plain_text",
				"text": "*{post_title}* was just published.  Check it out here: {post_permalink}",
				"emoji": true
			}
		}
	]
}

So my question – does the Webhook JSON carrier support block kit or am I just doing something wrong? thank you!