Designing options for my garden at the chook pen

The chook pen has had established gardens before. The beds were set out in rows and their current position gets a lot of sunlight and seems to have good drainage as they're positioned on a slope. I was tempted to stick with the layout that has been used before... until.. Robyn seduced me with mandala gardens and keyhole gardens and spiral herb gardens and all kinds of other permi-porn.

The benefit in having a garden bed that isn't a straight row is that you get more EDGE. Good 'ol Edge. You gain quite a lot more growing space when you extend the edge by adding curves and swirls and whatnot.
So, i am looking at a design that looks like a keyhole.. and duplicating it to form a mandala.
Here's a keyhole with the dimensions that work for being able to stand in the centre and reach the edges of the bed to plant and harvest:

I want to extend from one keyhole to a garden resembling this design: It reminds me of the Hunab Ku.

I have been thinking about edging it with river rocks that i collect from the creek. I kind of like the idea of collecting a heap of rocks to turn into garden edges.. There's something about using what's available in abundance locally, and using my own hands to select and move them and individually place them, that appeals more than if i were to just lay a log or something.
I've also been looking at making some fencing out of bamboo. There's a huge amount of bamboo available locally too, a lot of which was planted by Geoffrey and Case, guerrilla style.. with the foresight that the bamboo would provide great structural building options for people down the track.
As well as the mandala keyhole garden, I like the idea of having a spiral herb garden, just to see how it is to construct and how productive it may be with companion planting.

 The idea is that the centre is elevated so there are layers and different sized plants can fit on the different levels without interfering with each others' growth.
I want to do a herb spiral outside the kitchen area somewhere.