Make the pickled carrots first as they are better the day after they are made. Once the carrots are sliced put them in a colander and sprinkle them with salt. Toss the salt through the carrot and let it drain for at least 30 minutes.
Wash the carrots very well and drain again.
Put the carrots into a container or a large jar.
Meantime put the sliced ginger, vinegar and sugar into a pot and bring it just to the point where the sugar melts.
Pour the vinegar liquid over the carrots while it is just warm to the touch. If the liquid is too hot the carrots will cook. One in a jar or container store in the refrigerator.
Make the dressing in a large jar with a lid. Add the lime juice, sugar, fish sauce ( or soy sauce) garlic, ginger, chilli and chopped coriander roots. Shake well. Test the result. it should be sweet sour and salty. Let this stand in the fridge. It will keep for weeks like this.
Wash and drain the iceberg lettuce and break up into edible chunks. Sprinkle over all of the sliced onions, tomato, herbs. Drain the carrots a little and add some to the salad before tossing. You will only need 1/2 or even a 1/4 of them. Reserve the rest for another time
Drain the bits from the dressing and pour over the lettuce salad and toss well to cover the salad leaves in the dressing. Its best to dress just before you serve.