Adding custom shipping method for WooCommerce (v. 3.2.6)

woocommerce-custom-shipping-method.php

<?php
//Works with WooCommerce 3.2.6
add_action( 'woocommerce_shipping_init', 'econt_shipping_method' );
function econt_shipping_method() {
  if ( ! class_exists( 'WC_Econt_Shipping_Method' ) ) {
    class WC_Econt_Shipping_Method extends WC_Shipping_Method {

      public function __construct( $instance_id = 0 ) {
        $this->instance_id 	  = absint( $instance_id );
        $this->id                 = 'econt';//this is the id of our shipping method
        $this->method_title       = __( 'Econt Shipping', 'teame' );
        $this->method_description = __( 'Delivery to office of Econt Express', 'teame' );
        //add to shipping zones list
        $this->supports = array(
          'shipping-zones',
          //'settings', //use this for separate settings page
          'instance-settings',
					'instance-settings-modal',
        );
        //make it always enabled

        $this->title = __( 'Econt Shipping', 'teame' );
        $this->enabled = 'yes';

        $this->init();

      }

      function init() {
        // Load the settings API
        $this->init_form_fields();
        $this->init_settings();

        // Save settings in admin if you have any defined
        add_action( 'woocommerce_update_options_shipping_' . $this->id, array( $this, 'process_admin_options' ) );
      }
      //Fields for the settings page
      function init_form_fields() {

        //fileds for the modal form from the Zones window
        $this->instance_form_fields = array(

          'title' => array(
             'title' => __( 'Title', 'teame' ),
               'type' => 'text',
               'description' => __( 'Title to be display on site', 'teame' ),
               'default' => __( 'Delivery to office of Econt ', 'teame' )
               ),

          'cost' => array(
             'title' => __( 'Cost (lv)', 'teame' ),
               'type' => 'number',
               'description' => __( 'Cost of shipping', 'teame' ),
               'default' => 4
               ),

          );

          //$this->form_fields - use this with the same array as above for setting fields for separate settings page
      }

      public function calculate_shipping( $package = array()) {
	//as we are using instances for the cost and the title we need to take those values drom the instance_settings
        $intance_settings =  $this->instance_settings;
        // Register the rate
        $this->add_rate( array(
            'id'      => $this->id,
            'label'   => $intance_settings['title'],
            'cost'    => $intance_settings['cost'],
            'package' => $package,
            'taxes'   => false,
          )
        );
      }
    }
  }

  //add your shipping method to WooCommers list of Shipping methods
  add_filter( 'woocommerce_shipping_methods', 'add_econt_shipping_method' );
  function add_econt_shipping_method( $methods ) {
      $methods['econt'] = 'WC_Econt_Shipping_Method';
      return $methods;
  }
}