Place potatoes in a large pot and cover with cold water by 1 inch. Add 1 tablespoon kosher salt and bring to a boil over high heat. Reduce to a simmer and cook until potatoes are tender when pierced with a fork, about 15 minutes. Drain and let steam dry for 5 minutes - this helps them crisp later.

Preheat air fryer to 400°F. Arrange potatoes on a cutting board with space between them. Use the flat bottom of a measuring cup or sturdy glass to gently press each potato until flattened to about 1/2 inch thick. Some edges will crack - that is exactly what you want for crispy bits.

Brush or drizzle both sides of smashed potatoes with olive oil. Sprinkle with garlic powder, black pepper, and fine sea salt. Working in batches if needed, place potatoes in a single layer in the air fryer basket. Cook at 400°F for 12-15 minutes, flipping halfway through, until deeply golden and crisp at the edges.

Transfer to a serving plate immediately. Sprinkle with chopped parsley and flaky sea salt if desired. Serve hot - they lose their crispness as they sit.