the effort of clamping and unclamping , picking up the chainsaw and then cutting !!! why bother ?
Far easier to get a nice sharp hand axe and use that ... much faster and less effort.
The way I do it ;
get a nice big stump of wood , about 2 ft high , but that depends on how you work and how tall you are, then get the post to be pointed , hold in left hand at about shoulder height , approx middle of post !!, and place bottom end on stump . Then with the axe , in right hand , make a cut about 6" from the bottom . You angle the post so that the axe cut will in fact go towards the stump in a vertical line .Turn post 1/4 turn and repeat, repeat again till all sides are done .
It may take more than one swing of the axe to cut each side of the point , but take care and you will soon get the hang of it . Far less dangerous than using a chainsaw , your left hand is on the other side of the post to the axe at all times .
No clamping , no picking up and putting down of chainsaw , no refilling with petrol , although you may need to top up with tea every now and then !!!
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You can leave the bark on , but it may harbor insects that will munch away at your posts over time . Without treatment they may only last a few years . You can lightly burn the pointy ends in a bonfire , which will help protect them for some years , but they still snap at ground level anyway . But if they are free ... so what !!
Not sure if any of that makes sense ... but hope it helps a bit ...
cheers
Russ