I don't think you can really combine the two. Shelf-facing display just takes your CBC task and kind of makes the profiles look like they are on a shelf and you'd put the price below the profile (often replaced with a graphical image of the product).
In free format, you start off with a blank page and create the layout of your tasks, usually by using HTML table tags. Inside the cells of the table you use scripting functions to pipe in attribute and level labels from the design file.
Another way to put it is that shelf-facing display is kind of a one-click, fixed alternate way of displaying choice tasks, while free format is a start from scratch, do whatever you want (including a custom shelf display) on your own.
An example of free format CBC questions can be found in the help files at https://www.sawtoothsoftware.com/help/issues/ssiweb/online_help/index.html?hid_web_cbc_customcbc.htm.