Step 2: Cut Toward the Notch from the Other Side.

Picture of Cut Toward the Notch from the Other Side.
Cut from the other side toward the big notch.
When you get close to the notch the tree will start to lean away from you. If it doesn't, or if it leans the wrong way and binds your saw blade, have the Oompaloompas pull on the rope tied to the top of the tree.
I climb, prune and remove trees for a living and this looks like a disaster.  You would be better off hiring someone unless you have extensive knowledge of the different fiber strengths of different species.  Nearly every week I hear about another home owner who thinks they can do this safely and ends up dead, cutting off an arm or leg (or someone else's), or dropping a tree on a car or house.  I work with a chainsaw daily and it never ceases to amaze me the lack of respect that people have for these tools.  Chainsaws are not something to joke about and can cut your face in half before you know what is going on.  Google chainsaw accidents, go buy some chaps, hearing protection, safety glasses, boots, and gloves.  Use the saw for cutting up fire wood, I strongly urge you to not attempt felling trees. 
Oval5 years ago
The back cut should be horizontal, not on an angle as you are showing here.

You should wear eye and hearing protection when using a chain saw. I don't think it's a very good idea to be wearing shorts and there is no excuse for crocs, especially when operating a chain saw.

It's a good idea to use a VERY long rope, or have Oompaloompas sufficently fleet of foot so as not to end the day with Oompaloompas conciderably flatter than the ones you started with.