Combine Greek yogurt, olive oil, lemon juice, minced garlic, paprika, chili flakes, ground cumin, black pepper, and salt in a bowl. Add chicken thighs and coat thoroughly. Cover and marinate for at least 1 hour, preferably overnight.

Preheat the oven to 425°F (220°C). Toss halved baby potatoes with olive oil, garlic powder, dried oregano, salt, and black pepper. Arrange cut side down on a parchment-lined baking sheet. Roast for 25 to 30 minutes, flipping halfway through, until golden and crisp.

In a bowl, combine crumbled feta cheese, Greek yogurt, mayonnaise, lemon juice, minced garlic, and chopped dill. Mix or blend until creamy. Season with salt and pepper to taste. Adjust thickness with milk or water if desired. Chill until serving.

Heat a skillet over medium-high heat. Place marinated chicken thighs in the skillet and sear for 5 to 6 minutes per side, or until golden-brown and cooked through to an internal temperature of 165°F. Let rest a few minutes before slicing.

Arrange the roasted potatoes and chicken on serving plates. Spoon dill feta cream over the chicken and potatoes. Garnish with fresh chopped parsley or dill. Serve hot.