Render form in block

<?php
namespace Drupal\mymodule\Plugin\Block;
use Drupal\Core\Block\BlockBase;
use Drupal\Core\Form\FormBuilderInterface;
use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
/**
* Provides a submitblock block.
*
* @Block(
*   id = "mymodule_submitblock",
*   admin_label = @Translation("SubmitBlock"),
*   category = @Translation("Custom")
* )
*/
class SubmitBlock extends BlockBase implements ContainerFactoryPluginInterface {
 /**
  * The form builder.
  *
  * @var \Drupal\Core\Form\FormBuilderInterface
  */
 protected $formBuilder;
 
 /**
  * {@inheritdoc}
  */
 public function __construct(array $configuration, $plugin_id, $plugin_definition, FormBuilderInterface $form_builder) {
   parent::__construct($configuration, $plugin_id, $plugin_definition);
   $this->formBuilder = $form_builder;
 }
 
 /**
  * {@inheritdoc}
  */
 public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
   return new static(
     $configuration,
     $plugin_id,
     $plugin_definition,
     $container->get('form_builder')
   );
 }
 
 /**
  * {@inheritdoc}
  */
 public function build() {
   return $this->formBuilder->getForm('Drupal\mymodule\Form\SubmitForm');
 }
 
}