The trickiest cut when building a chair or stool is leveling the feet. This cut is always a wacky compound angle. And when you combine a compound angle with a foot that is an odd shape, such as the octagon shown here, it can be difficult to keep your saw in the right plane.
Here’s how I do it – it’s a method that has yet to fail me.
Lay out the cut you want to make on all the facets of the leg. I use a mechanical pencil so the line is a consistent width and easy to see.
Making this cut is a lot like drawing a line in the sand at the beach. If you draw a shallow ditch in the sand with your finger, the ocean will follow that ditch because it is the path of least resistance.
So think of your saw as water.
Make a shallow kerf (about 1/16” deep is fine) on all the leg’s facets or surfaces that you can see.