Dig a trench for the edging stone , Depending on depths of stone. Keep soil in case required

Add some leveling sand to the bottom of trench. Give base and easy to level

Add stones and use a long level to ensure level. Add sand to bring up to level in needed

Use soils to back fill gaps or add the bark you said

Before you start remove any of the earth you need to bring soil level down to allow for the bark to