Monte Carlo, Markov Chains, Metropolis Hastings.
For example, say this is a brand new coin and I don’t have any prior knowledge, I can use a uniform distribution — U(0,1) as prior distribution, since p(Head) can be any number in [0,1]. Randomly drew θ from U(0,1) and θ = 0.43, then the prior p(θ) is p(0.43) = 1 since f(x) =1 for all x in [0,1]