Place the turkey breast in the crockpot.
Sprinkle with poultry seasoning.
In a bowl, stir together cranberry sauce, onion soup mix, orange juice, and apple cider. Pour over the turkey.
Cover and cook on Low for 6–7 hours or until the turkey reaches 165°F.
Let rest before slicing
After the turkey is done, strain through a mesh strainer and pour the juices from the crockpot into a saucepan.
Bring to a gentle simmer.
In a small bowl, whisk together 2 tbsp cornstarch + 2 tbsp cold water until smooth.
Slowly whisk the slurry into the simmering juices until it thickens into a glossy gravy.
Taste and adjust — add a splash more cider for brightness or if you want a sweeter gravy, or a pinch of salt if needed. If you want to make it more savory add stock: Stir in ½–1 cup chicken or turkey stock while simmering the juices. This stretches it and balances the sweetness! Throw in a sprig of fresh thyme while it's simmering to bring an herbiness to it
