Start at the butt end there is very little weight on it easier than bucking it on the ground worse case you need a wedge.
If you start at the butt you will change the balance with all of the weight still in the top. The trunk could rise, or roll, or shift and break the crotch, or hang up in the air where its a tall reach to cut.
The upper branches are hanging out there just waiting to be cut to length with a pole saw. Then it's just a short pull to drop the trunk onto the ground.
Philbert