How to create an unfair coin and prove it with math: https://izbicki.me/blog/how-to-create-an-unfair-coin-and-pro...
Basically, it proves that creating a biased coin really is impossible.
one cannot, for example, weight a coin so that it is substantially more likely to land “heads” than “tails” when flipped and caught in the hand in the usual manner. Coin tosses can be biased only if the coin is allowed to bounce or be spun rather than simply flipped in the air.
TL;DR: if you want unbiased coin IRL, make sure you catch it before it hits the ground.