Nope, not what they're doing at all. They provide both the methodology and data on their site.

Two problems. First, their methodology isn't consistent. i.e., Hong Kong scores a 90 in property, which means "private property is guaranteed," even though Hong Kong is a nation where government literally owns all the land and land rights are leased without right to renewal rather than owned. So how is private property guaranteed in a country with no private ownership of land?

Second, a lot of their methodology has nothing to do with freedom in the libertarian sense. For instance, including positive freedoms (like infrastructure) rather than simply just negative freedoms.

Honduras is also docked points because of land deed fraud. Shouldn't that be an issue of "buyer beware"? Shouldn't it be the responsibility of the buyer to trust that the land deed is valid before making a purchase? That would be like docking America freedom points because of the popularity of Amway and Bitcoin and the Home Shopping Network.

Heritage is engaged in circular reasoning: They're claiming that that free countries are more successful, but they're also defining freedom to mean success. Which again, is akin to the KKK making a white slam dunk index that includes Michael Jordan.

I have doubts about the validity of the WFF's slavery index (just give it a quick google, multiple non-partisan sources say the methodology is severely flawed).

And all of the criticisms of the WFF index can be applied even moreso to Heritage. At least "slavery" has a much clearer meaning than a nebulous concept called "freedom."

That said, France is ranked higher than Qatar in the categories pertaining explicitly to personal freedom (rights and lack of corruption).

There is no accounting for personal freedom, or else Singapore's draconian conservative laws where it's illegal to buy chewing gum without a doctor's prescription.

Slavery falls under labor, where Qatar scores 71.2 and France scores 43.5.

Honduras is docked points for failing to protect people from gang violence (even though Honduras has a booming private security industry, which should be the libertarian way). But Qatar isn't docked points for failing to protect people from literal slavery.

Qatar's higher overall ranking is seemingly because of less stifling business regulations and (especially) much lower levels of government spending and public debt.

Yes, because a country with a highly regulated minimum wage is so much less free than a country with unregulated literal slavery.