How hashing the roll sequence can eliminate bias: (strongest practical debiasing)
Concatenate the rolls (as a string, list of numbers, or bytes) and feed them into a cryptographic hash such as SHA-256. The hash acts as a randomness extractor: even modest per-roll bias or slight statistical imperfections are mixed away by the avalanche effect. As long as the total min-entropy of the input is at least the desired output length (128 or 256 bits), the hash output is computationally indistinguishable from uniform random bits.