How to machine on both sides of the material?

Hey everyone. I am trying to machine some handles. They require two sided machining. I managed to create one relief for front (cutting perfectly) and another for back (cutting perfectly). 

However, the problem is when I turn the material the holes don't match. Back side is a bit tilted so hole from the back does not match the hole on the front. 

How could I do reliefs such that their frontal part exactly matched their back side? 

My material is a square, so shouldn't be a problem with me turning it. and I have a square angle clamp, so it sits in the same spot.