Free markets almost never work.
When have we had a free market in history? Reviewing Hamilton's call for the constitution, he discussed in depth how taxes were collected from trade in a variety of republics. Dating back through history. So when have we had a truly free market?
Slavery was about as close to a 'free market' in labor as you could get. Remember, 'free market' means that government does not interfere with 'market forces'. In a free market the economy is allowed to do whatever the markets allow it to do. If buying, selling, owning, working human beings is profitable, and thus in line with 'market forces',
then in a 'free market' it is allowable. Government intervention to abolish slavery, for reasons in direct conflict with 'market forces', was a direct attack on the 'free market'.