Starting from primitive shapes (Shane Olson's workflow)
Created from a single reference illustration... + anatomy knowledge ;-) !
3D character sculpting based on the beautiful art of illustrator Clio Wolfensberger
https://www.artstation.com/artwork/GXv33Q Game workflow using Zbrush, 3D Coat (UVs+retopo) and Marmoset Toolbag (baking).