The title is a lie; these are oven-baked potato parts. A complicating factor is the different bake temperatures which may not be possible if there are other dishes competing for oven space.
The tablespoon of oil per potato might be a bit high, though most of it will cook into the potatoes given time.
Chop russet potato to something like a french fry shape; I leave the skin on. Soak in icy water for around 20 to 30 minutes. Crush and add a vitamin C pill to help prevent browning? Lacking ice, park the potatoes outside or in a fridge, if that is suitable and available. The water bath removes starch which helps produce a crispier fry.
Drain and dry the potato well, mix with the oil and garlic salt. Save the towel from the drying step to get the oil off your fingers.
Cook potato at 300F for TODO minutes. Remove potato, let oven come up to 400F, and cook for TODO more minutes. Not sure on the timing yet, or what signs to look for the 300F potatoes being suitably done, at least 15 minutes, probably more like 25 to 30? 400F potatoes are done when browned suitably. The potatoes likely can be parked for some amount of time after the first cooking.
A 10" skillet in the oven will result in the potatoes being crowded which probably is not ideal and likely increases the cooking time. So if possible spread the potatoes out on a baking sheet to ensure that they are not overly crowded.
A thicker cut on the potatoes will give more contrast between the interior and exterior texture.
Another method involves a 10" skillet with lid; in this case the potatoes are steamed in their own liquid with lid on, then cooked at a higher heat with the lid off, after they have cooled from the first cooking. Batches will likely be necessary to avoid overcrowding in the skillet for the second cooking at higher heat.
The potatoes may be broken up more than in an oven bake on account of them being moved around in the skillet. A french fry shape is not ideal, quartering the potato then cutting fairly thick rows makes for easier wedges to deal with.
Preheat skillet, season with around one tablespoon of oil per potato and garlic salt. Add potato, reduce heat, and cook for 15 to 20 minutes with the lid on. Cool the potatoes, the cook on high heat until browned, flipping potatoes as need be. Cook with the lid partially on if the potatoes are not fully cooked through.
Microwave the cut potatoes for about five minutes, then let cool, then do the high temperature oven roast.