Here are a few things I learned:
Taller sides will make it easier to keep the chickens out and harvest the veggies. This will also allow more room for filler material like a hugelkultur, and if I put the filler in over the rainy season, it will be moister for when we put the soil on top. Given that the harvest produces lots of extra organic matter, I think starting it now is a good idea.
Winter rains will help with this.
To that end, I started making posts. I'm experimenting with a tool called a froe and am trying to rive a cottonwood tree I chopped down (so I could destroy a nasty tent caterpillar nest).
I really don't think I have the hang of it as the froe kept wondering to the side. But I have a few posts and plan to try a different kind of tree to see if that makes things easier.
It just filled up way too fast for us, I've had to build it up to make enough room for compost until we can make the new bin.
We considered making this next one out of rock (there certainly is enough of it about) but decided to construct it out of compostable materials so that it will be easier to break apart and rebuild in 5 to 10 years.
For logs, the split is started with an axe or wedges and is oriented in the brake so that the split is close to parallel to the ground. With the froe blade centered on the log and parallel to the ground, drive the froe into the log with a wooden mallet and then lever the froe to advance the split. As the split advances, use a wedge behind the froe so the split does not close on the froe.
If the split starts to wander off-center you can re-center it as shown in the diagram below. Be sure to keep the tip of the advancing crack close to or directly on top of the lower support log for this correction process and press down on the lower part as you rotate the froe to advance the split.
and a post about riving black Locust