A coin is more likely to land on the side that was initially facing up. Nearly 51/49. Random link explaining this here.

Does this affect the randomness of this posts suggested method? If so… how can we ensure randomness in the physical world?

Casino dice?

I have my own doubts about trusting any hardware/software solution for randomness. I also don’t trust myself to recognize true randomness because I know my brain is designed to detect patterns, even when they don’t exist.