How do I cut an accurate mitre?
The best method for cutting accurate mitres of whatever angle is to make a relevant mitre box. This mitre cut is usually followed by a shooting board to get a crisp meeting point.
Small mitre box
Large miter box
For cleaning up long mitres, people sometimes use a donkey’s ear shooting board, but that is quite a specific tool for a specific purpose, so I’m not sure we’ll be covering it.