There are many ways to cut deep slots in wood. One popular method is to use a band saw. However, this method can be time-consuming and difficult to use. A better option is to use a jigsaw.
Jigsaw blades are available in a variety of depths, so you can easily cut deeply into the wood. You can also use a router to create deep slots in wood. However, routers are more difficult to control and can be more challenging to use than a jigsaw or band saw.