"parent": [ "woocommerce/checkout-shipping-methods-block" ],
"attributes": {
	"lock": {
		"type": "object",
		"default": {
			"remove": true,
			"move": true
		}
	}
}

setExtensionData(
	'namespace-of-your-block',
	'key-of-your-data',
	value
);

// block.js
export const Block = ( { checkoutExtensionData, extensions } ) => {
/**
	 * setExtensionData will update the wc/store/checkout data store with the values supplied. It
	 * can be used to pass data from the client to the server when submitting the checkout form.
	 */
	const { setExtensionData } = checkoutExtensionData;
}

// ... Some code here

useEffect( () => {
/**
	* This code should use `setExtensionData` to update the `key-of-your-data` key
	* in the `namespace-of-your-block` namespace of the checkout data store.
*/
setExtensionData(
	'namespace-of-your-block',
	'key-of-your-data',
	value
);
}, [ setExtensionData, value ] );

use Automattic\WooCommerce\Blocks\Integrations\IntegrationInterface;

/**
 * Class for integrating with WooCommerce Blocks
 */
class Custom_Inner_Block_Blocks_Integration implements IntegrationInterface {

	/**
	 * The name of the integration.
	 *
	 * @return string
	 */
	public function get_name() {
		return 'new-field-block';
	}

	/**
	 * When called invokes any initialization/setup for the integration.
	 */
	public function initialize() {
		// ... Some code here: (e.g. init functions that registers scripts and styles, and other instructions)
	}

	// ... Other functions here
}

use Automattic\WooCommerce\Blocks\Package;
use Automattic\WooCommerce\Blocks\StoreApi\Schemas\CartSchema;
use Automattic\WooCommerce\Blocks\StoreApi\Schemas\CheckoutSchema;

/**
 * Your New Field Block Extend Store API.
 */
class Custom_Inner_Block_Extend_Store_Endpoint {
	/**
	 * Stores Rest Extending instance.
	 *
	 * @var ExtendRestApi
	 */
	private static $extend;

	/**
	 * Plugin Identifier, unique to each plugin.
	 *
	 * @var string
	 */
	const IDENTIFIER = 'new-field-block';

	/**
	 * Bootstraps the class and hooks required data.
	 *
	 */
	public static function init() {
		self::$extend = Automattic\WooCommerce\StoreApi\StoreApi::container()->get( Automattic\WooCommerce\StoreApi\Schemas\ExtendSchema::class );
		self::extend_store();
	}

	/**
	 * Registers the actual data into each endpoint.
	 */
	public static function extend_store() {
		if ( is_callable( [ self::$extend, 'register_endpoint_data' ] ) ) {
			self::$extend->register_endpoint_data(
				[
					'endpoint'        => CheckoutSchema::IDENTIFIER,
					'namespace'       => self::IDENTIFIER,
					'schema_callback' => [ 'Custom_Inner_Block_Extend_Store_Endpoint', 'extend_checkout_schema' ],
					'schema_type'     => ARRAY_A,
				]
			);
		}
	}

	/**
	 * Register the new field block schema into the Checkout endpoint.
	 *
	 * @return array Registered schema.
	 *
	 */
	public static function extend_checkout_schema() {
		return [
            'Value_1'   => [
                'description' => 'A description of the field',
                'type'        => 'string', // ... type of the field, this should be a string
                'context'     => [ 'view', 'edit' ], // ... context of the field, this should be an array containing 'view' and 'edit'
                'readonly'    => true, // ... whether the field is readonly or not, this should be a boolean
                'optional'    => true, // ... whether the field is optional or not, this should be a boolean
            ],
			// ... other values
        ];
	}
}

<?php
/**
 * Plugin Name:     New Field Block
 * Version:         1.0
 * Author:          Your Name Here
 * License:         GPL-2.0-or-later
 * License URI:     https://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain:     new-field-block
 *
 * @package         create-block
 */

// ... Some code here

/**
 * Include the dependencies needed to instantiate the block.
 */
add_action(
	'woocommerce_blocks_loaded',
	function() {
		require_once __DIR__ . '/custom-inner-block-blocks-integration.php';

		// Initialize our store endpoint extension when WC Blocks is loaded.
		Custom_Inner_Block_Extend_Store_Endpoint::init();

		add_action(
			'woocommerce_blocks_checkout_block_registration',
			function( $integration_registry ) {
				$integration_registry->register( new Custom_Inner_Block_Blocks_Integration() );
			}
		);
	}
);

// ... Some code here

private function save_shipping_instructions() {
	/**
	 * We write a hook, using the `woocommerce_store_api_checkout_update_order_from_request` action
	 * that will update the order metadata with the shipping-workshop alternate shipping instruction.
	 *
	 * The documentation for this hook is at: https://github.com/woocommerce/woocommerce-blocks/blob/b73fbcacb68cabfafd7c3e7557cf962483451dc1/docs/third-party-developers/extensibility/hooks/actions.md#woocommerce_store_api_checkout_update_order_from_request
	 */
	add_action(
		'woocommerce_store_api_checkout_update_order_from_request',
		function( \WC_Order $order, \WP_REST_Request $request ) {
			$shipping_workshop_request_data = $request['extensions'][$this->get_name()];
			$alternate_shipping_instruction = $shipping_workshop_request_data['alternateShippingInstruction'];
			$other_shipping_value           = $shipping_workshop_request_data['otherShippingValue'];
			$order->update_meta_data( 'shipping_workshop_alternate_shipping_instruction', $alternate_shipping_instruction );
			$order->save();
		},
		10,
		2
	);
}