Thicker trunks with ground contact at both ends
If the trunk has contact with the ground at both ends, the trunk’s upper surface is exposed to compressive strain. This means that the guide bar will get pinched if you try to saw through the whole trunk from the top. The following method requires that you use a larger saw with a long guide bar.
Start by cutting about 1/3 of the trunk diameter on the side you are standing. Lean slightly forwards and stand a bit to the side of the cut.
Now cut about 1/3 of the trunk diameter from the top.
Lean over the trunk and cut about 1/4 of the diameter from the opposite side.
Make a bore in the lower part of the trunk. Now saw down through the trunk. Avoid sawing into the ground.
Finally, saw the undercut from the bottom up until the trunk breaks or you reach the corresponding cut from the top.
Safety first! Pay close attention to how the trunk is reacting at all times.
Cutting using a felling wedge
An alternative method for cutting a thick trunk on the ground is to use a felling wedge.
Cut the trunk from above until the guide bar and the tip of a felling wedge fit in the cut.
Let the saw remain in the cut. Knock the felling wedge in the cut as far as possible without the tip reaching the guide bar.
Cut down until about 1/4-1/3 of the diameter of the trunk remains.
Knock the wedge in as far as possible. Now saw the rest of the log. Avoid sawing into the ground.