Put 50g instant rice noodles in a bowl and cover with boiling water, leave to stand for 3 mins, drain then rinse in cold water and drain well. Squeeze juice ½ lime into a jar along with 1 tsp fish sauce. Put 50g mango pieces on top, then add the noodles. Slice 1 carrot into ribbons with a vegetable peeler and pile on top of the noodles.
Fill the rest of the jar with ½ small pack mint, ½ small pack coriander, 1 tbsp salted peanuts and pinch chilli flakes. Put the lid on and store in the fridge for up to one day. When you want to serve, tip everything out into a bowl and mix well. Add soy sauce to taste, if you like.