Prepare the ingredients – Peel and thinly slice the potatoes, chop the onion, and dice the ham.
Mix the sauce – In a bowl, combine the cream of mushroom soup, water, garlic powder, salt, and black pepper.
Layer in the slow cooker – Add a layer of potatoes, followed by onions, ham, cheese, and sauce. Repeat until all ingredients are used.
Cook on low – Cover and cook for 6 hours or until the potatoes are tender and creamy.
Check and stir (optional) – If desired, gently stir halfway through for even cooking.
Add extra cheese – In the last 30 minutes, sprinkle extra cheese on top for a golden, melty finish.
Let it rest – Turn off the slow cooker and let it sit for a few minutes before serving.
Serve and enjoy! – Scoop onto plates and pair with your favorite main dish.