How to call custom twig file to render the content?

 <?php

    Step #1: Define hook_theme in .module file
    function MODULE_NAME_theme($existing, $type, $theme, $path) {
      return [
        'my_template' => [
          'variables' => ['var_test' => NULL],
        ],
      ];
    }

    Step #2: Call the Template
    /**
     * @file
     * Contains \Drupal\MODULE_NAME\Controller\TestTwigController.
     */
     
    namespace Drupal\MODULE_NAME\Controller;
     
    use Drupal\Core\Controller\ControllerBase;
     
    class ModuleNameController extends ControllerBase {
      public function content() {
     
        $renderable = [
          '#theme' => 'my_template',
          '#var_test' => 'variable test',
        ];
        $rendered = \Drupal::service('renderer')->render($renderable);
     
      }
    }

    Step #3: Create Twig Template
    //the file name would be my-template.html.twig
    <p>Test twig template!</p>
    <p>test_var: {{ var_test }}</p>

    Remember to Clear the cache.
   ?>