I need to make a raised garden and would like to use flat stone as the wall. Is it just a matter of buying the stone and neatly piling them up?

I am making the garden on the lawn and the area is firm, level, and solid. Should I just start placing the first layer right on the lawn? Does one need to pack between the rocks with cement or sand? If not will watering cause the dirt to wash out the wall?

Lastly... will the pressure of the soil and compost press the walls out?

Thanks! Any help is surely appreciated.

Ken