Grease the insert of your slow cooker with non-stick cooking spray or butter to prevent sticking.
Wash and peel the potatoes. Slice the potatoes very thinly and uniformly. Consider using a mandolin slicer for best results.
In a medium saucepan, melt the butter over medium heat. Add in the onion and garlic and cook until translucent. Sprinkle the flour over the top and stir constantly to cook the mixture until lightly golden brown, about 2 minutes.
Gradually whisk in the chicken broth and heavy cream until smooth. Stir in the dried oregano, paprika, salt, and pepper. Continue cooking, stirring constantly, until the sauce thickens, about 3-4 minutes.
Layer one third of the sliced potatoes in the bottom of the greased slow cooker insert. Pour a third of the sauce over the potatoes followed by a third of the cheddar cheese and a third of the ham. Repeat the layers two more times.
Cover the slow cooker and cook on low heat for 4 to 5 hours, or until the potatoes are tender and the sauce is bubbly and creamy.
Once cooked, sprinkle with chopped fresh parsley for a pop of color and freshness, if desired.
Notes
I found that Yukon Gold potatoes work best with this recipe. Other varieties will work, but may not be as creamy or hold their shape as well.If the top sauce has separated a little bit when the potatoes have cooked, just stir it back together until it is uniform and creamy again. The potatoes are finished cooking when they are tender and no longer translucent looking. Timing will vary a bit based on how thick you cut the potatoes as well as how hot your slow cooker runs.If the potatoes are done before dinner is ready, switch the slow cooker to the 'warm' setting for up to an hour.