Creating a thumbnail Navigation for a Flexslider
Install Flexslider module
If you need to display images as a view, select "slider w/thumbnail controlnav pattern" option set in Flexslider display mode settings.
If you displays images a multi-valued image field, select "slider w/thumbnail controlnav pattern" for the field in Manage display tab.


Please note that controlNav pattern (you mentioned) is not the same as thumbnail slider.