flexslider_add() doesn't accept string name of option set as valid value

I'm trying to use Flexslider from within my module. Given that I've created an optionset called 'spotlight' and the following HTML:

<div class="spotlight">
<ul>
<li><img src="" alt="" /></li>
<li><img src="" alt="" /></li>
<li><img src="" alt="" /></li>
</ul>
</div>

How do I enable Flexslider? I tried:

<?php
flexslider_add('spotlight', flexslider_optionset_load('spotlight'));
?>

but this doesn't work. It took me a while to figure out that flexslider expects a optionset as Object instead of a string as the documentation suggests. And that ID (although the function accepts NULL), needs to be set even if you only need an optionset. I'd expect the module to work without ID, as I prefer using classes in my HTML instead of ID's. But if this is needed, can you please explain how my HTML should look and how I can load the Flexslider?

Thanks a lot!