Hi Meric,
A File System in Flash is not recommended practice, therefore Freescale does not provide an example for that, As you may know, since a file system is very intrusive and does a lot of data verification, it might damage the flash or in the best scenario it will reduce life cycle and endurance.
I just found an old sample code that uses MFS mounted over the MCU flash, it usesa ColdFire device (MCF5225x) with an old MQX version. You may need to port this application to current tools, but I strongly recommend to reconsider your applications requirements,
Best regards,
Carlos