Fill a large pot with 6 cups water. Add 1 tablespoon kosher salt and ½ teaspoon baking soda. The salt seasons from inside out. The baking soda raises pH, breaks down pectin on potato surface, and creates rougher texture for maximum crispness. Bring to rolling boil over high heat. Add whole, unpeeled Yukon Gold potatoes. Boil 15-18 minutes until fork-tender but not falling apart. Insert paring knife into center of largest potato—if it slides in with minimal resistance, they're ready.

Drain potatoes in colander. Don't rinse—keep alkaline surface intact. Shake colander gently to remove excess water. Spread potatoes on clean kitchen towel or baking sheet lined with paper towels. Let air-dry for 5 minutes. This step is critical—surface moisture is the enemy of crispness. The drier the potato, the faster Maillard reaction begins in air fryer.

Preheat air fryer to 400°F (204°C) for 5 minutes. Transfer dried potatoes to clean cutting board. Use bottom of glass, small plate, or potato masher to gently press down on each potato. Flatten to about ½ inch thick (1.3 cm). Crack the skin and create irregular, rough edges without smashing so thin they fall apart. Goal is to maximize surface area without destroying structure. Rougher edges = more crispy spots.

Brush both sides of each smashed potato with avocado oil using pastry brush or hands to coat evenly. In small bowl, mix garlic powder, smoked paprika, and black pepper. Sprinkle seasoning blend over both sides of potatoes. Don't add fresh garlic or herbs yet—they'll burn during high-heat cook.

Arrange smashed potatoes in single layer in preheated air fryer basket. Don't overlap. Leave about ½ inch space between each potato for air circulation. Close basket and cook 12 minutes at 400°F (204°C). Don't open during this time. At 12-minute mark, open basket and flip each potato with thin spatula. Bottoms should be deeply golden brown with crispy, lacy edges. If not, cook 2 more minutes before flipping.

Once flipped, brush tops with melted butter. Close basket and cook another 10-12 minutes at 400°F (204°C). Total cook time is 22-24 minutes. Check at 20-minute mark. Potatoes should be golden brown on both sides with visibly crispy edges. For darker color, add 2-3 more minutes.

Remove potatoes from basket and transfer to serving platter. While still hot, sprinkle with fresh chopped rosemary and thyme. Add generous pinch of Maldon sea salt flakes. Heat will release essential oils in herbs. For garlic herb butter version, melt 1 tbsp butter with 1 minced garlic clove and drizzle over finished potatoes. For cheesy variation, sprinkle grated Parmesan over hot potatoes. Serve immediately while edges are crackling.