So the augment kit is what creates the slot in the first place, then the augment is something different? And where do augments come from?
Yeah to your first sentence.
Augmentation kits are crafted by players. Augments are crafted by players too. Next time you're at a global trade network terminal use the pull down menu to look up: Item modifications > augments
Or type in Advanced Skill Augment to the search box to see a more limited list for examples.