In the above picture Tyson Schultz is creating what is called a "Humbolt notch". You might want to compare this notch with an open-face or other conventional notches at the following Department of Labor site. Making the Cuts - OSHA
"Starting the bottom cut of the face, notice how I begin on the side of the tree rather than the front. It is easier to line your cuts up if you begin by making an intersection of cuts. All you do is pull your saw out of the top cut and tilt the bar down."