Make the Felling Cut
Score a line connecting the apex of the notch on both sides for a cutting guide. The back cut should be parallel and even with the apex of the notch. Then make the felling cut. The instant the tree begins leaning, pull the saw free, set the chain brake and walk away along one of your escape routes, keeping an eye on the tree so you can react if it doesn't fall the way you planned. Never take your eye off a falling tree.