I use this in my template override (item.php)

<!-- Item title -->
<h2 class="itemTitle">
<?php if(isset($this->item->extraFields->Ondertitel)): ?>
<!-- Item edit link -->
<span class="itemEditLink">
<a class="modal" rel="{handler:'iframe',size:{x:990,y:550}}" href="<?php echo $this->item->extraFields->Ondertitel->value; ?>">
<?php echo JText::_('K2_EDIT_ITEM'); ?>
</a>
</span>
<?php endif; ?>

<?php echo $this->item->title; ?>

<?php if($this->item->params->get('itemFeaturedNotice') && $this->item->featured): ?>
<!-- Featured flag -->
<span>
^{<?php echo JText::_('K2_FEATURED'); ?>}
</span>
<?php endif; ?>

</h2>

Using the extrafield alias name.

It then gives this page just displaying this single extrafields list, with links to the item.

marleensboekvandeweek.nl/alle-boeken

The menu calls the K2 Categorie, where I switch more or less everything off. Also deleted some extra code out fo the PHP files but it should work with the standard one too.