A simple LittleFS wrapper and example implementation using the SpiMemory library. I haven't seen anyone post an example implementation of this working, so I decided to give it a crack.
This depends on ARMmbed's LittleFS and Marzogh's SPIMemory Arduino library. Pull both of them into your Arduino library path.
I tested this on an Adesto AT25SF041 flash IC and an ATSAMD21G18-based Arduino Feather clone (Cortex-M0+ based).