In Franz Josef Options > General > Slider, set the Slider content option to Full content.
When you do this, you might want to create a post category specifically for the posts to be displayed in the slider, and then hide that category from appearing anywhere else by setting the Franz Josef Option > General > Slider > Exclude the categories from posts listing option to Everywhere.
After that, it’s simply manually adding the buttons to the slider post:
The button styles can easily be applied by giving the links the following classes: