public function add_metaboxes() {

		// metabox defaults
		$defaults = [
			'context'  => 'advanced',
			'priority' => 'default',
		];

		$metabox = array_merge( $defaults, $this->struct );

		add_meta_box(
			'metabox-' . $this->id(),
			$metabox['name'],
			[ $this, 'create_metabox' ],
			$metabox['screen'],
			$metabox['context'],
			$metabox['priority']
		);

	}