Although I geekily enjoyed the numbers in the fertility chapter, what I wish I'd read four years ago was Crawford's simple advice for starting a forest garden from scratch.  First of all, he recommends that you kill all of the weedy perennials (like brambles and trees) before doing anything else --- that tip alone could have saved me lots of pain and suffering.  Simply mowing regularly for a year or two usually does the trick.

Assuming your blank slate consists of a grassy field, Crawford recommends planting the canopy trees, then slowly kill mulching bands of earth to be filled with smaller plants a year later.  On Crawford's large scale, plastic landscape fabric makes sense as the kill layer, but for most of us, I'd instead recommend simple kill mulches made of cardboard and woody mulches as a way of boosting our soil fertility and keeping microorganisms happy.  Regardless of what you use to kill the grass, Martin's technique is a bit like the "islands that merge" pattern in Edible Forest Gardens, which I've adopted as my own method of building a forest garden.

The benefit of this a-bit-at-a-time system is that you can slowly propagate all of the extra plants you need, filling in one area per year, while maintaining the parts you haven't gotten to yet with a few yearly rounds of mowing.  Alternatively, you can till the space up and plant a perennial cover crop to take the place of grass in areas waiting to be planted with the permanent understory.  (Or grow vegetables there.)

Using this technique, Crawford estimates you'll need to devote about 5.5 days per 1,000 square feet of forest garden during the design and establishment phase.  (Maintenance takes him another 2 days per 1,000 square feet per year.)  Your final forest garden will have all the pieces in place after two to ten years, and he tells us not to worry if the forest garden doesn't look like much at first.  Photos on the internet of Crawford's garden suggest that it's quite possible to create a beautiful and productive space using his methods if you just keep plugging right along.