(Rather like Stonelifter would if he saw my attempt at building a garden wall).

Gardenwallbuilder used to be a term of derision. A bit like 'put up by a farmer'. But it's not any more. Remember just to use stone - no bricks, no cement and certainly no soil. Also remember it leans inward - broader at the bottom than at the top. And use a short heavy hammer both to break the stones, for fill, and handle first to tighten up the face. I guess twenty odd years of practise would be useful too. Take the most time getting a good selection of stone and work with an excess, so there's plenty to chose from.