Preheat oven to 210ºC conventional.
Peel kumara and dice into 3cm cubes. Place on prepared tray and drizzle with olive oil. Season with oregano, salt and pepper.
Place the chicken thighs in an ovenproof dish. Crush the garlic and zest the orange, then sprinkle over the chicken. Juice the orange into a small bowl. Add olive oil, mustard, honey and vinegar. Drizzle half of the dressing over the chicken and set the rest aside.
Roast chicken and kumara in the oven for 40 minutes. Baste chicken halfway through cooking.
In the meantime, prepare the salad by dividing spinach on plates, slicing orange, celery, avocado, and dicing feta. Assemble on top of the spinach.
Slice chicken thighs and top salads with kumara and chicken. Drizzle with remaining dressing before serving.
