f3s_start (f3s_service_t *service,
           f3s_flash_t *flash)

This function passes the service and flash arrays to the filesystem component so it can make calls to the socket and flash services, and then starts the driver. This function returns only when the driver is about to exit.

When writing your main.c, you'll need to enter:

If you have a system with only one socket consisting of the same flash devices, then there will be only a single entry in each array.