Here is an excellent picture that contains info on the subject.
Here is the best way to get 6x of a single skill:
1. Spam til you get a 6 slot card
2. Reroll the skills until all of them are in a talent/skillset that is NOT what you are aiming for, so if you're going for an archer card, get magic skills for example.
3. Start rolling for your skills one at a time, in this order: 2, 3, 4, 5, 6, 1.
I thought about it a lot and that would be the best way to get a nicely rolled card spamming a single type of skill. You want to save the first slot for last since by that point you'll have the lowest chance of getting the same skill again, so it'll be nice to not have to reroll it and only land the skill.