Here is a step by step instructional of how I built my sauna door. 
Note there are no measurements on here because your door can be any size that you want it to be within reason. 
You will need access to a full woodworking shop to do this proficiently- table saw, jointer, planer, some sort of domino or dowel joiner, router. 
Does not include how to hang a door that is not prehung, how to make the handle, or how to attach the ball latch.  
 
Doors are one of the more challenging woodworking projects and require precision, proper material selection, and an understanding of wood movement. Many factors—such as humidity, joinery, and milling—can affect the final result. By purchasing these plans, you acknowledge that I am not responsible for issues such as warping, movement, or structural failure.