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 even more crazy, just take $10 in pennies, shake them in a bucket, dump them out and line them up. Not sure how many bits you would need, so I just guessed $10 would be enough (1000 pennies).
That's far too many. You only need $2.56 as long as all the coins are "fair" and are not intrinsically predisposed to land on a particular side.