We built these planter boxes from Jarrah end pieces found at an auction. They are solid and heavy.
I was inspired by mdstorrs's Tall man raised garden bed for vegetables and my son built the boxes after I modified the design. He isn't a carpenter but did a beautiful job. Luckily we live near Bunnings, he needed an impact drill and new drill bits for the Jarrah. He planned everything and made templates for the drill holes.
The planter box is 40cm deep, and the bottom board covers the base. The salvaged posts we used were not square, and many of the boards were either shorter or bent in places, but the garden beds still look terrific.
We put Jarrah wood chips in first for drainage, then pea straw, sheep manure, and then layers of good soil with sheep manure.