Preheat the oven to 375 degrees F (190 degrees C).
Combine ricotta cheese, Parmesan cheese, Italian seasoning, and salt in a small bowl and set aside.
Season chicken thighs on both sides with garlic powder and salt.
Heat olive oil in an oven-proof skillet over medium-high heat. Place chicken thighs, smooth-side down in pan and brown, 3 to 4 minutes. Flip thighs over and remove skillet from heat. Top each thigh with an equal amount of ricotta cheese mixture. Spoon marinara sauce over the ricotta cheese and around the chicken thighs.
Bake in the preheated oven until chicken is no longer pink in the center and the juices run clear, about 25 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Remove from the oven and leave oven on.
Top chicken with mozzarella cheese and return to the oven until cheese has melted, 2 to 3 minutes. Garnish with parsley and serve.
