Real coin flips are ~49-51 not 50-50 https://www.scientificamerican.com/article/scientists-destroy-illusion-that-coin-toss-flips-are-50-50/
But you can guarantee equal probability with a simple trick! Flip 2x in a row starting with the same side up.
HT->call it H
TH->call it T
HH,TT->try again
(due to von Neumann https://en.wikipedia.org/wiki/Randomness_extractor#Von_Neumann_extractor)
This leads to randomness extractors: from a given random process, what's the biggest uniform distribution you can get efficiently?
Randomness extractors give another interpretation of #entropy:
avg # bits needed to *describe* the outcome
=
# uniformly random bits you can *extract* from the outcome