How are the skirting boards mitred correctly?

The skirting boards are the widest at the bottom. They are slightly oblique to make them more attractive. This has an effect when cutting. Clamp the skirting board firmly so it can't move when you are cutting it.

Put the skirting board upright in the mitre box, like you would put it against the wall, and rotate the saw to the left or right depending on the angle you want to obtain.

If you are working with an electric circle saw whose motor you can turn left or right, put the skirting board flat on the saw bench with the design side up. This method is the most practical because it allows you to attach the skirting boards easily.

With the clip skirting boards, you need to hold the supplied wooden spacer under the skirting (with the thickest edge under the skirting) in order to obtain a perfect mitre. Otherwise, the same guidelines as above apply here too.