In a large bowl combine the carrots, cucumbers and daikon.
In a small jar or container with a lid, combine the rice wine vinegar, fish sauce, sugar, sambal, ginger and garlic. Shake well and let sit for at least 15 minutes to allow the sugar to dissolve and the flavors to marry.
Toss the cucumber-daikon mixture with the vinaigrette and let sit outside the fridge for an hour before serving. Sprinkle with the scallions.