Easy way to draw fischer projection of a simple 3d stucture

This concept is purely based on how good you are imagining things. Prospective matters the most. Select any representation you are comfortable with, and then convert it into Fischer Projections. If you need to convert 2D to 3D then it is simple , horizontal lines in 2D projections are bonds coming outwards(towards you) and the vertical lines are the bonds going inside the plane(away from you).
vice and versa for 3D to 2D.

It is like IUPAC, if you practice more the better you get.