If you have rounded or irregular stone, this video shows how to work with that situation:
Building with Round Stone.
For really round stone like cobbles, or New Hampshire granite boulders, I have seen stones split in half or so to give some toothy edges to form stable walls. Batter needs to be even more than "standard" 1:6 for this sort of material. A wall of all small cobbles might need to be as wide at the base as it is tall with a 1:4 or more extreme batter.