How to get slick slider working well on multi-directional(RTL/LTR) site?
This is possible by implementing template_preprocess_slick


use Drupal\Component\Serialization\Json;

/**
* preprocess variables for slick.html.twig templates.
*/
function template_preprocess_slick(&$variables) {
  $language = \Drupal::languageManager()->getCurrentLanguage();
  if($language->getDirection() == 'rtl') {

    $settings = $variables['content_attributes']->offsetGet('data-slick');
    if(!empty($settings)) {
      $settings = Json::decode($settings->value());
      $settings['rtl'] = true;
      $settings = Json::encode($settings);
      $variables['content_attributes']->setAttribute('data-slick', $settings);
    }
  }
}