Wash and scrub potatoes, then cut into large 2–3 inch chunks.
Boil in salted water for 8–10 minutes until edges soften; drain and steam dry.
Shake in colander to rough up the edges.
Heat olive oil with garlic and thyme in roasting pan while oven preheats to 425°F (220°C).
Remove garlic and thyme, then add potatoes to hot oil and toss to coat.
Roast 40–50 minutes, flipping once or twice, until golden and crispy.
Sprinkle with parsley, flaky salt, and pepper; serve hot with optional sour cream or lemon wedges.