Find out Center of the wall
While using stud finder, look for the wall center where you want to fix the iron center, when you decide the location mark it by using led pencil. For straight draw you can use a level, draw a perpendicular line down the center of the wall.
Pick up the Jab saw and start cutting square board according to outline of the template. Cut it large enough so that your arm could move freely around the board without any obstruction. Finish up the cutting when inside of the wall is clear to you.
Apply Stain on the door
Wear your rubber gloves and apply stain along with wood grain. Keep on applying till it gets as level as it could. When you are done with stain and door surface is fully covered with it, now use cloth rag and clean the excess. Now let it dry and then stain the other side of the door.