I would do all the work from the top of the berm. No overhead work. Maybe work from both sides of the trunk depending on pole saw blade size and trunk size. Don't work on a dangerous tree while alone.
1. Clear the top of the berm on both sides of the trunk for a safe work space.
2. Standing on the berm with a powered pole saw, undercut the trunk on one side of the berm, whichever side is most convenient to work.
3. Make a top cut. Nibble at it if needed until the trunk is severed.
4. Continue cleanup process with two less dangerous parts.
Bruce
1. Clear the top of the berm on both sides of the trunk for a safe work space.
2. Standing on the berm with a powered pole saw, undercut the trunk on one side of the berm, whichever side is most convenient to work.
3. Make a top cut. Nibble at it if needed until the trunk is severed.
4. Continue cleanup process with two less dangerous parts.
Bruce