I simply leave a 1kg tub out on the side and let it fully defrost - this takes about 3-4hours. Once defrosted, or virutally defrosted and divided it up into 4 x 250g portions. Cut each daily 250g portion in half as Millie is fed twice a day. Each 250g portion is stored in a little tuppaware container and kept in the fridge. It stays fresh 4 days and 1kg lasts 4 days, so works out rather nicely.
I have also, part defrosted a 1kg container and divided it all into 125g portions, wrapped in greaseproof paper and put back into 2 empty 1kg containers and refrozen. This way, if ever I have a need for a quick individual serving, I have access to it and it will defrost very quickly.
You can serve the food straight from the fridge, part frozen or frozen, but NI recommend allowing your dog to get used to the food first before offering frozen.
The above sounds a bit complicated, but honestly its not. Every 4 days I just defrost the food, divide up and store in the fridge.