Ff + Slice = FF

When used by a breeding's poster (or in a split, the split partner), one whelp in the litter may have an allele removed. 

You cannot remove a dominant allele on a recessive gene (aka you can't remove a F from flaxen to make Ff.)

This should be used either in the litter image stage (via the description or via a comment) or in the geno design request stage, so long as it is applied by the breeding's poster. Dice or its modified version, 20 Sided Dice, can only be used once per litter, though both Dice and Slice may be used and can be used on different whelps in the litter.