There are a few old salts in these parts that swear that freezing your flour (and all your other dry provisions) kills the weevil eggs. When I stocked up my boat, my friendly local supermarket did me the favour and froze everything to -30° for 48 hours. Once thawed, it all got recanted into plastic 2 litre coke bottles, because they're waterproof and UV protected. I have a total of about 50 bottles stashed all over the boat.

The bottles are washed in a solution of Miltons and then left in the sun for two days too dry.