Custom Query by Author field and meta

By adding another array

   $args = array(
      'post_type' => 'custom_post_type',
      'meta_query' => array(
        array(
            'key'     => 'size',
            'value'   => 'big',
            'compare' => 'LIKE',
        ),
        array(
            'key'     => 'gender',
            'value'   => 'male',
            ),
      )

);
$query = new WP_Query( $args );