The title says it all. I have tried ToastConfig.DefaultPosition = ToastPosition.Bottom but that has no effect. I have also tried setting the position every time I toast also to no avail. I've found other people with the same issue but never found an answer. I was hoping someone on here had encountered a similar issue and worked around it. I might add that the toasts work and look as expected on iOS and Android.
The author said that this is the intended design on UWP which I think just means he doesn't want to fix it. I ended up just making a custom control which is added as a UI element to the pages you want to toast. Not the most elegant solution but certainly the most customizable solution.