Before packing in the soil to the trench, another coat of preservative was applied particularly to the inside surfaces and joins. This design for the raised bed was simply based upon the best wood available at the wood shop, 100mm by 28mm. 150mm would have worked also.
The soil originally removed from the trench was used to pack in around the posts and bottom lengths of wood. This heavier soil ensured the posts and frame were well packed into the ground, inside the frame and outside.
It is not ideal to disturb a raised bed. For example they should not be walked upon as soil compression defeats the purpose of the bed. In this case, disturbance could not be avoided. Still, some care was taken in refilling the bed and levelling it out. Later I will add a layer of compost to the top soil of the bed before planting.
The key point in constructing a raised bed is to ensure the overall bed is level. This is for aesthetic reasons and practical reasons, ensuring the bed looks level with surrounding structures and ground levels, and ensuring even drainage across the bed. With a feed of compost and a crop of beans and other nitrogen fixers this year, the bed should restore its own organic soil structure over the next year.