You have to knap the stone to fit the lock. There are general specs for each size lock. The leather should come to the end of the upper and lower jaw.
Some rocks work better bevel up, some down. depends on the lock.
Sorry bro there isnt a one size fits all answer.
This was the first flint that was in my lock. As you can see the leather is too long. I was in a hurry to touch her off