Cash in Ancapistan

Money provides such an advantage over barter, that it is indispensable for a functioning economy today. Modern civilization has been accustomed to a government or pseudo-government entity creating and maintaining a money supply. Indeed, these currencies have dominated the economy across the globe throughout living memory. Recently, cryptocurrencies have been on the rise, but they are far from replacing dollars, pounds, and yuan. In a truly free society, how would money be provided for the economy?