If you can make the assumption that alien creatures have a concept of three dimensions (and later in his article he flips the question around and asserts they d

If you can make the assumption that alien creatures have a concept of three dimensions (and later in his article he flips the question around and asserts they do [since they sent us 3d blueprints]) then it's a relatively simple task. The author said you can't draw pictures, use gestures or images to show the aliens, but that doesn't mean you can't have the aliens use their own imagery. So, to explain left handedness: Picture a 3D coordinate system. With X, Y, and Z axis. Vector is represented by the notation of (X, Y, Z). Draw a vector (0,0,1). This is the "Forward" vector. Draw a vector (0,1,0). This is the "Up" vector. Cross vector (0,0,1) with (0,1,0). The resultant vector (-1,0,0) is the "Left" vector. For all points Y, and Z of -X (not including 0) lie to the "Left" of the plane ZY. We don't need to convey a sense of forward and upwards as to how it relates to the alien beings--only how it relates to the coordinate system.