Wedges more than half way in, on both sides (cutting from 12:00 to 6:00, place wedges at 4:00 and 8:00, when the stump comes free, it will open the keft. If not, you can hop on the stump and try to break it free levering over the wedges as fulcrums.
If I have a 40" stump and a 36" bar, I dog...