I am trying to create this in WPF (I realize I could just use an image, but I am trying to learn WPF):
(source)
This is what I have so far but it is
So a stackpanel will place the first item at the top, the second just below it, third below the second, and so forth. What you could do is use a Canvas or a Grid. Like the stackpanel, they are "Content Controls" and support placing multiple objects inside of them like you have done with the stackpanel.
So a really quick way to do what you're trying to accomplish would be: