Preheat oven to 400°F and set your oven rack to the top half. Set aside a large baking sheet.
Scatter potatoes and tomatoes across the baking sheet. Add chicken breasts in the middle a few inches apart. Rub chicken breasts with 1 tablespoon oil.
Sprinkle minced garlic, oregano and thyme across pan. Add salt and pepper to taste.
Drizzle the rest of olive oil evenly across. Toss to mix well. Place several lemon slices on top of chicken.
Butter a piece of parchment paper, and cover the chicken and vegetables with buttered parchment paper (butter side facing down)
Bake for 22 to 25 minutes, adding green beans for the final 10 minutes. If the chicken looks pale, you can always put it under the broiler for the final 3 minutes.
Check doneness by inserting an instant-read thermometer into the middle of the chicken breast. Remove from the oven as soon as it reaches 160°F (71°C). Alternatively, as soon as clear juice starts to seep out of your chicken breasts, it means that they are cooked through.
Remove the chicken to a serving plate or carving board. Cover with foil and let it rest for 5-10 minutes to let the juices redistribute through the meat before serving.