Dan I have the same question!
The only how-to I ever seen was posted on a Euro bowyer's site. The best I could gather from the pictures was he ground two 36" lams of light colored wood like maple to a .20 thickness. He had three other woods, all varying in contrast and different widths. Lets just say they were Osage, cocobolo and bacote. He also ground all woods to a .20 thickness.
He then laid down one 36" long light colored lam, then on top of the long lam he glued the colored woods in order...
Osage,coco,bacote,coco,Osage,..coco,bacote,coco, Osage, over and over until the 36" light colored lam was covered. He then glued the other 36" light colored lam on top of it all.
This is what I took from the pictures, but if anyone has actually done this, I sure would like to learn how to do this the correct way!
When dry, he cut the riser on a curve and glued this (lam sandwich) into the riser.