Preheat air fryer to 400° Fahrenheit. Wash 4 medium russet potatoes well under running water and scrub with vegetable scrubber to remove any surface dirt. Use paper towels to dry each potato completely then place potatoes on cutting board.
Carefully poke each potato with tines of fork, creating small vent holes over entire potato surface. Gently rub entire surface of potatoes with 1 tablespoon neutral oil, then sprinkle coarse sea salt over all sides of potatoes.
Place salt-crusted potatoes in air fryer basket, working in batches as needed if using especially large potatoes or if air fryer is small. Place basket in preheated air fryer and cook potatoes 30 minutes.
After 30 minutes, remove basket from air fryer. Test potato doneness by poking potatoes with tines of fork - fork should easily pierce skin and inner flesh of potatoes. Note: If fork does not easily pierce potatoes, return basket to air fryer. Cook potatoes another 5 minutes, then check doneness again. Repeat as needed until potatoes are ready.
When potatoes are ready, remove basket from air fryer and carefully transfer potatoes to cutting board.
Slice potatoes down center with knife, being careful not to cut potatoes completely in half. Gently press on sides of potato to open center slice and allow steam to escape.
Use fork to fluff insides of potatoes, then dress baked potatoes with desired toppings and serve immediately.