Feature post metabox and query

feature-post-query.php

<div class="posts-listings">

<?php
 $args = array(
			'posts_per_page' => '1',
			'orderby' => 'featured-checkbox',
			'order' => 'ASC',
			'meta_query' => array(
                      array(
                      'key' => 'featured-checkbox',
                      'value' => 'yes'
              )
          )
		 );

     $featured_query = new WP_Query($args);
?>

<?php
  while ($featured_query->have_posts()) : $featured_query->the_post();
?>
<div class="posts-items">
  <div class="item-image">
    <?php if ( has_post_thumbnail()) : ?>
       <a href="<?php the_permalink(); ?>" title="<?php the_title_attribute(); ?>" >
         <?php the_post_thumbnail(); ?>
       </a>
     <?php endif; ?>
  </div>
  <a href="<?php the_permalink(); ?>" class="posts-title">
    <h2><?php the_title(); ?></h2>
  </a>
  <?php the_excerpt(); ?>
  <a href="<?php the_permalink() ?>" class="read-more">Read More...</a>
</div>
<?php endwhile; ?>
</div>

<div class="posts-listings">
<!--Add all non-featured posts-->
<?php
  $args = array(
			'posts_per_page' => '1',
			'order' => 'ASC',
            'meta_query' => array(
                array(
                    'key' => 'featured-checkbox',
                    'compare' => 'NOT EXISTS', //or "NOT EXISTS", for non-existance of this key
                )
            )
		 );

     $page_query = new WP_Query($args);
?>

<?php
  while ($page_query->have_posts()) : $page_query->the_post();
?>
<div class="posts-items">
  <!--DO MORE STUFF HERE -->
</div>

feature-post.php

<?php
  
  
/**
 * Adds a meta box to the post editing screen
 */
function ns_featured_meta() {
    add_meta_box( 'ns_meta', __( 'Featured Posts', 'ns-domain' ), 'ns_meta_callback', 'post', 'normal', 'high' );
}
add_action( 'add_meta_boxes', 'ns_featured_meta' );

/**
 * Outputs the content of the meta box
 */
function ns_meta_callback( $post ) {
    $prfx_stored_meta = get_post_meta( $post->ID );
    ?>

 <p>
    <span class="row-title"><?php _e( 'Check if this is a featured post: ', 'ns-domain' )?></span>
    <div class="row-content">
        <label for="featured-checkbox">
            <input type="checkbox" name="featured-checkbox" id="featured-checkbox" value="yes" <?php if ( isset ( $prfx_stored_meta['featured-checkbox'] ) ) checked( $prfx_stored_meta['featured-checkbox'][0], 'yes' ); ?> />
            <?php _e( 'Featured Item', 'ns-domain' )?>
        </label>

    </div>
</p>

<?php
}

/**
 * Saves the custom meta input
 */
function ns_meta_save( $post_id ) {

  // Checks save status - overcome autosave, etc.
  $is_autosave = wp_is_post_autosave( $post_id );
  $is_revision = wp_is_post_revision( $post_id );
  $is_valid_nonce = ( isset( $_POST[ 'ns_nonce' ] ) && wp_verify_nonce( $_POST[ 'ns_nonce' ], basename( __FILE__ ) ) ) ? 'true' : 'false';

  // Exits script depending on save status
  if ( $is_autosave || $is_revision || !$is_valid_nonce ) {
      return;
  }

  // Checks for input and saves - save checked as yes and unchecked at no
  if( isset( $_POST[ 'featured-checkbox' ] ) ) {
      update_post_meta( $post_id, 'featured-checkbox', 'yes' );
  } else {
      update_post_meta( $post_id, 'featured-checkbox', 'no' );
  }

}
add_action( 'save_post', 'ns_meta_save' );