Heat the oven to 200°C. Put the peppers and potatoes on half a baking tray and drizzle with plenty of olive oil, sprinkle with plenty of salt and pepper and use your hands to toss and make sure everything is coated in oil. Put in the oven for 20 minutes. Put the meatballs in a bowl with the harissa paste and a good drizzle of olive oil, toss to coat. Add the meatballs to the other half of the pan. Return to the oven for another 20 minutes.
While everything cooks put the feta and yoghurt in a food processor and blend until smooth.
Use a knife to check the potatoes are cooked through. When everything is ready put a dollop of hummus in the bottom of a bowl, top with some of the meatballs, peppers and potatoes. Add some olives if using and drizzle everything with the feta sauce.
Nutrition information is an estimate and will vary depending on the exact ingredients used.