How to design a flat design wizard?

We are migrating our modal based wizards to be "flat" and included in the main navigation system. They should be accessible via a navigation bar. How do we place the different buttons and explain the user that he is inside a wizard process? How do we prevent the user to exit the wizard before completing it? (or at least explain that he should complete)?

Are there real-life examples? All I found are modals that are disconnected from the product's navigation system.