>>Can I have a suggestion regarding my purpose?
Yes, to understand how the memory and file systems work, and how they will interact. Or work with someone who has history implementing such systems.
You're implementation would need to be in the DISKIO function layer, and would need to manage the block write and erase where the size of the write replaces a portion of the content from the existing data within a larger erase block. You would need to manage the erase, and any spanning issues related to the IO request. Typically this would require a RAM holding buffer of at least the size of the erase block within the device.
There is not an example because it is quite complex to achieve and test thoroughly, and general programing skills aren't sufficient to pull it off effectively.
FATFS would be better applied to eMMC memories on the STM32 platform, as these are basically soldered down SD Cards, and manage block write/erase tasks internally.
