Wouldn't it be more efficient to just use 10 sided dice? This way you can skip some conversions?
Since you are trying to create a 256 bit number typically represented as either Hex or base58, wouldn't it be more efficient to use either:
sixty-four 16-sided dice, or eighty-six 8-sided dice, or one hundred twenty-eight 4-sided dice?
Or a single standard deck of cards.