The Creators Update of Windows is coming soon. One of the new features coming with it is a way to keep your UWP app on the screen above all other windows. It’s called CompactOverlay mode, but you probably know it better as Picture-in-Picture.
First you want to check and see if CompactOverlay mode is supported:
Then you’ll want to switch to the CompactOverlay mode. In this example it’s based on a click of a button
What this will give you is a small window containing your app! That’s the first step. From here you can customize the experience by specifying the height and width of the window: