Preheat the oven to 425°F (220°C).
Place the chicken breasts onto a baking tray and add 2 tablespoons of the olive oil, along with the lemon juice, lemon zest, harissa paste, and honey. Season with salt and pepper and toss together until the chicken is well coated.
Add the sweet potatoes, onion and chickpeas to the tray, and toss with the remaining 2 tablespoons of olive oil. Arrange everything in an even layer, lay the lemon slices over the chicken and place the tray into the hot oven.
Roast for 40-45 minutes, tossing halfway through, until the chicken is cooked through and the potatoes are golden.
Serve warm, topped with the feta cheese and olives.
