Before revision:   I detail a possible scenario involving actin/myosin layers in snails (and in  C. elegans ), and outline other mechanisms which might govern handedness in eukaryote cell motility and in plants .
After revision:  It seems particularly easy for handedness to emerge in a shear or rotation in the background of an effectively two-dimensional system, such as the cell membrane or a layer of cells, as this requires no pre-existing axis apart from the layer normal. I detail a possible scenario involving actin/myosin layers in snails (and in C. elegans ), and outline other mechanisms which might govern handedness in eukaryote cell motility and in plants .