Shim the one-way FIRST...so that you have just a tiny amount of play side-to-side...without the crown gear in the case.
Put the crown gear (the little one) in the case, then the one-way.
Move the shims from side to side until you have very little lash (free play) between the one-way and the crown gear.
Both boxes, shaft and spur holder must be in place and assembled to check the lash, because the shaft holds the crown gear in place.
I don't run any shims on the crown gear. Even one will make it jam into the one-way gear and bind.