1Add beets, oil, vinegar, honey, coriander seeds, peppercorns, and 1 teaspoon salt to slow cooker.
2Cover and cook on low until beets are tender, about 6 hours.
3When beets are cool enough to handle but not still hot, peel them using paper towels to wipe skins from the flesh. Cut them into wedges and toss with dressing.
4Dressing: Whisk together 3 tablespoons fresh orange juice, 2 tablespoons extra-virgin olive oil, 1 tablespoon balsamic vinegar, 1 teaspoon honey, salt and pepper in a small bowel and reserve for step 3.
5To serve, place watercress on a large platter, scatter with the beets and dressing and sprinkle with pistachios on top.