In a small bowl, mix 6 tbsp olive oil with 2 tbsp red wine vinegar, the mustard, and the salt. Add some freshly ground black pepper.
With the aid of a mandoline, finely shred the cabbage. Place the shredded cabbage in a bowl and mix in the dressing. Let sit (in the refrigerator) for at least 15 minutes.
With a vegetable peeler, peel the beet thinly. With the aid of the mandolin, thinly slice the beet. Place the beet slices in a bowl and add 1 tbsp olive oil, 1 tbsp red wine vinegar, and some salt. Let sit (in the refrigerator) for at least 15 minutes.
Cut the onion in half and slice thinly. In a small bowl, mix the onion with 1 tbsp red wine vinegar and some salt. Let sit for about 10 minutes.
Peel the oranges, remove the white pith and slice the oranges horizontally.
Assemble the salad right before serving. Put the red cabbage slaw on a large serving plate (or use 4 individual plates). Arrange the beet and orange slices on top. Garnish with the onions, almonds, feta, and fresh herbes. Grind over some black pepper. Serve with crusty bread to soak up the juices.