Planing the stool tops
Every stool top is flattened by hand before it is oiled. Here is why we still use a plane for it.

Every stool top is flattened by hand. A machine would be quicker, but a hand plane leaves a surface that takes oil evenly and shows the grain without sanding marks.

Rough shaping is done with a saw first; the plane only takes off the last millimetre, in long, even curls when the blade is sharp.
Caring for an oiled top
Wipe spills with a damp cloth. Once a year, rub in a thin coat of hard-wax oil and buff it off after twenty minutes.