1. Peel the outer layer of the watermelon radishes if thick. With a sharp knife or mandoline, thinly slice the radishes into rounds.
2. Sprinkle sea salt over the radishes in a colander set over a bowl. Cover and set aside for at least 20 minutes.
3. Drain radishes, and lightly pat dry. Arrange the slices on a serving platter or individual plates.
4. Make the vinaigrette by whisking together the orange juice, avocado oil and fresh herbs. Add a pinch of sea salt and black pepper to taste.
5. Toss the arugula with half the dressing. Place a handful of dressed arugula on top of the sliced radishes and top with a few slices of avocado.
6. Garnish with crumbles of fresh goat cheese if desired and drizzle the remaining dressing over the top of the radishes. Serve immediately.