"Best" way to produce a Spider Axanthic would be breeding a Spider Het Axanthic to a Het Axanthic or a Spider Het Axanthic to an Axanthic.
The Spider het Axanthic to an Axanthic has pretty good odds at 1 in 4 of producing the combo, but there are no guarantees.....out of 18 eggs in 2 clutches of that breeding I only hit on onebut that's better than none.
Preshed pic:
Hope that helps.