Is it possible to rewrite a Flash page after an interrupted write?
This should have all the info you need: https://cseweb.ucsd.edu/~swanson/papers/DAC2011PowerCut.pdf

It seems to say that you should be safe since your flash uses single level cells.

Considering writes are a pretty fast operation, I think you should dodge the problem instead. I don't know how your power distribution is done, but if your board is powered from, say, 5V which then feeds a 3V3 LDO or switching regulator, then a capacitor of suitable value on the 5V rail would still power the board as its voltage drops down to 3V3 plus LDO dropout voltage. 

Same if you have an old school transformer-rectifier-cap supply. Make sure you start the write when the supply smoothing cap is at its max voltage.

If your board is powered from a wall wart, well these would have a high voltage capacitor carrying mains voltage, which should be able to power your board for at least a couple tens of milliseconds, which should be enough. In this case, you could use a simple detector on the mains voltage, and start the write when the mains voltage is above a certain threshold. Even if you lose mains voltage, the HV cap will have enough stored energy to finish the write if it has enough µF.