Prep: Lightly grease a 4–6 quart slow cooker with nonstick spray or oil.
Layer: Spread the diced potatoes evenly across the bottom. Scatter the diced onions in a layer over the potatoes, then top with the sliced hot dog rounds.
The "No-Stir" Rule: Cover and cook on HIGH for 3–4 hours or LOW for 6–7 hours. Important: Do not stir for at least the first 2 hours. This allows the potatoes to brown against the ceramic insert.
Incorporate: After 2 hours, gently stir the mixture, scraping up any browned bits from the bottom and sides—this creates the "gravy" that coats the hash.
Finish: Continue cooking (stirring once or twice more) until the potatoes are fork-tender and the onions have melted into the mixture.
Serve: Give it a final stir to distribute the juices and serve hot directly from the crock.