"Mercantilism". Big Government projects funded by taxpayer money (mostly from the Southern States at that time.)
Henry Clay was the primary proponent of "Mercantilism", but it is really just an offshoot of Hamiltonian philosophy.
The Hamiltonians believed in using government power to stimulate industry and economic interests. They wanted an activist government that taxed a lot and spent a lot, especially if it went into the pockets of their cronies.
So, how and why ought the North’s laws and policies that favored industry and free labor have been disfavored, while the South’s policies favoring slavery ought to have been favored and defended?
Mercantilism is another matter and refers to the practice in that era of monarchies and nation states building their economies through protectives tariffs that forced the development of domestic industries. Adam Smith's insight was the free trade was generally better because offered general economic prosperity though comparative advantage. Predatory trade policies are an exception of sorts and raise of host of other issues.
In fairness to Hamilton, as the first Secretary of the Treasury he put America's finances on a sound footing. His fundamental insight was that if properly organized and regularly paid, America's national debt would become an economic asset by paying interest on currency reserves held by banks and the wealthy. This helped create the pool of capital that funded the country's development, then and now.
This may seem counter intuitive, but the national debt and the debt market and banking system it fosters are part of the reason that you can get a home mortgage and a car loan and that you have an employer who will hire you. They enable banks to act as intermediaries so that wealthy people can convert cash into a source of income through capital investment. In effect, lending to build and provide you (and the rest of us) with a home, car, a job, and an abundance of material goods and services is not charity or state socialism but income generating capital investment.
The alternative to Hamilton's system that you seem to suggest that the Confederacy offered was that instead of providing investment capital to fund internal improvements and productive jobs and better living for free people, the bulk of investment capital would go to funding the purchase and holding of slaves laboring under conditions of money-saving privation. That is mostly accurate, but keep in mind that since slavery also required capital, its financiers made a lot of money. In the end, the bankers and the wealthy always make money somehow.