Not necessarily the best way to capture Hayek's thought on this subject. But it is Hayek in his own voice discussing the "twin concepts" of evolution and spontaneous order. In this 1990 paper "The Theory of Spontaneous Order and Cultural Evolution" published in the journal Cultural Dynamics, I make my own effort to lay out these ideas. Given the recent work by David Sloan Wilson to separate the "Hayek monster" from Hayek the scientist/scholar/thinker of relevance, it is important to think about these ideas in a subtle and critical way.
Of course, we have Hayek's words on these subjects in various essays in Studies and New Studies, but also in works such as The Constitution of Liberty, Law, Legislation and Liberty, and The Fatal Conceit. Since his intellectual task was to "use reason to whittle down the claims of reason" and to "demonstrate to men how little they really know about what they imagine they can design" it isn't clear to me that radical implications for political economy and social philosophy are understood by critics even if we can disentangle Hayek from the political appropriation of him by various pundits and politicians through the years.