Place beef, pork, and lamb in a large mixing bowl. Season with salt and pepper. Add wine, parsley, juniper berries, garlic, bay, carrots, onions, leeks, and thyme. Mix together, cover with plastic wrap, and refrigerate overnight or up to 2 days.
Rub a crockpot with duck fat, if using. (You may add 2-4 tbsp olive oil, if you are not using the fat) Layer potatoes, marinated meat, and vegetables in the pot, seasoning between each layer with salt and pepper, ending with a layer of potatoes. Pour in remaining marinade and arrange the bacon, overlapping the slices slightly, over the top. Add the additional white wine.
On high for 4-5 hours or low for 8-10 hours. Enjoy.