The free market has existed ever since early tribes began to trade with each other and among themselves when they began to realize that humans had diverse sets of individual skills. Please, for the love of God, open a history book.
No. The free market is an 18th century concept that only found support later on and absolutely doesn't fit with the economy of early tribes.
Early tribes are either hunter-gatherers, who have such a simple lifestyle that makes it hard to even talk about an economy at all, and early agricultural peoples, who are only slightly better. Neither of these groups have any place for "diverse sets of individual skill" because these peoples are focused on survival and employ all of their resources into either agriculture for the settled peoples or hunting and gathering for the nomadic and semi-nomadic peoples (and the few odd sedentary hunter-gatherers).
With the development of further agriculture sometimes a surplus can be created that eventually leads to the development of urban societies and civilization, which is the kind of polities that have existed from Ancient Sumer, passing through Rome, up to Louis XIV's France. All these polities still have in common the same fundamentals: the overwhelming majority of the population works in the field to produce the agricultural surplus necessary to feed everyone and also support advanced urban society. Most of the population is forced to work in the field, in highly collectivized rural communities, because agriculture demands it and without it there's no civilization. People do not have a free choice, even if there weren't serfdom or slavery or whatever awful system of government control people would come up with, because the fundamental economic system in pre-industrial societies doesn't allow for individual freedom as we understand it in modernity. It's intrinsically only something a few elite can enjoy.
People struggle to understand how fundamentally the industrial revolution changed human society to its very core.
Mercantilism was the top-down system that relied upon slavery, rather than the free market system that had essentially existed for some 10 or 20 thousand years or whatever.
No, mercantilism is about maximizing exports and minimizing imports with the aim of not having to rely on foreign imports while having other people buy your goods, with the government playing a major role in ensuring that national interests and protection of national goods are ensured. Slavery isn't necessarily part of the picture, but mercantilism is a 17th century European economic theory and all European trade empires traded in slaves, so...
Also, as explained before, the free market is at most as old as Adam Smith, and only ever makes sense as an economic system for industrial societies. That's 300 years while being way too much generous.
The only economic system that has endured and has staying power, is a free, fair, and open market where the vast majority of the population freely makes choices as to what they need or want, and can find the appropriate merchants who have the skills, abilities, and ambition to fulfill their needs in exchange of something else.
However, slaving societies dominated large parts of Eurasia from Sumer to Louis XIV, and are clearly way older and have existed for much longer than any system where "the vast majority of the population freely makes choices as to what they need or want", because these other societies only came into existence very recently.
I'll have to repeat myself, but this is important: the modern ideas of people choosing the profession they want, living where they want, with their individual worth having a great deal of importance even if they're not economically or politically important are all modern concepts brought forth by 18th and 19th century economic and political revolutions that changed radiacally the way society worked. Egyptian peasants under the Pharaoh had no chance in life except staying peasants unless absurd luck came their way, and Medieval peasants several millennias later were in the same situation, but at least agriculture had got somewhat more reliable thanks to technology.
It's why slavery failed. And it's why the US and Britain came out on top.
While having slavery themselves?
Britain developed its industrial revolution well before outlawing slavery, and while profiting off it.
It seems that Spain went into decline apparently because of slavery, not the fact that they kept importing tons of silver without realizing that "inflation" isn't just a fetish on DeviantArt, and then Britain took their place, even though they were the guys who brought slavery to North America to begin with.
Make it make sense.
Chattel slavery as practiced in the western world in this timeframe was a fantastic failure, and only lasted for a very short time in the annals of human history.
Well, it was a fantastic failure, morally speaking, but practically speaking it actually lasted a very long time, definitely more than the lifespan of actual free trade economies, and was seemingly sustainable enough to survive through antiquity and the Medieval world even with the new Abrahamic religious clearly disliking the institutions because Christianity tried to make it illegal for Christians to enslave other Christians, and that prohibition barely worked even in the Middle Ages, and Islam tried to limit the practice of slavery to non-Muslims only as well, and there was endless abuse on their end of things as well.
This is such a slop of messy, politically-infused historical misconceptions and ideological nonsense.