Initialize a Select render array with the result of a Entity Query #drupal8

Select-SiteList.php

// Load user information
$user = User::load(\Drupal::currentUser()->id());
$tempList = $user->get('field_user_sites')->referencedEntities();

$sitesId = array();
if (count($tempList) > 0) {
  foreach ($tempList as $site) {
    $sitesId[] = $site->id();
  }
}

$sitesEntities = SiteEntity::loadMultiple($sitesId);

$optionArray = array();
foreach ($sitesEntities as $site) {
  $siteCode = $site->get('field_site_code')->getString();
  $siteName = $site->get('name')->getString();
  $optionArray[$siteCode] = $siteName;
}

$form['location'] = array(
    '#type' => 'select',
    '#title' => $this->t("Location"),
    '#size' => 60,
    '#multiple' => 'true',
    '#search' => 'true',
    '#options' => $optionArray
);