You might just be interested to be positive and watch development, or you might like to be more active, and help real developments, which will take not much of your time, but patience as the trees grow. Other plants can be harvested sooner. A forest garden only reaches maturity after 20, 30, 40 years or more!
There is an excellent example of a Forest Garden in Belgium. It has been going for 40 years, so it is quite mature! at:
AND - they have also created a human system of cooperators, for skills exchange, seed exchange, and to ensure the future continuation of their systems. The initiators are now 80+ years old! :
http://fraternitesouvrieres.over-blog.com/
According to Robert Hart, a forest garden consists of 7 distinct layers.
1 - Tall, light demanding trees
2 - Short, shade tolerant trees
3 - Shrub layer
4 - Herbaceous layer
5 - Plants that spread horizontally
6 - Rhyzosphere - root plants
7 - Vertical layer - climbing plants
+ 1 - Mycorrhiza (mushrooms / fungi under the soil)
And of course, there is the animal life - birds and bees etc in the air, worms and insects, bacteria and fungi, in the soil, and those insects that like to run up and down plants, such as ants.
And of course - there is TIME - over the years the form of a forest garden will change as trees grow and reach maturity.
A natural output of good forest gardening is that the soil becomes more rich, and more healthy, and able to hold water and air better.
The forest garden of Graham Bell, in Scotland is 800 meters square. The one at Mouscron is 1800 meters square.
I am currently exploring, "what is the smallest effective forest garden?" - both as a square or round, OR more as a relatively thin, but more or less long form.
I estimate, that for a "round or square form", an absolute minimum to support the interactions between the plants is a diameter / side length of 4 meters. For "thin but more of less long form", a depth of a minimum of 3 meters, with a length of 5 meters might be the minimum - only experience will tell, and it may vary from location to location.
Using "dwarfing root stocks" for the fruit trees, might allow the smaller forest gardens to work better than using standard root stocks.
In a town or city, with community involvement and access to one or more forest gardens, perhaps the most important outcomes are individual and social, though "free organic fruit and vegetables" is nice too.
"Ancient" (traditional) varieties might also interest some people - often they are more robust, taste better, and have higher nutritional content than "modern commercial-industrial varieties".
"Sustainability is based on diversity" might be also a thought that arises - particularly interesting in this time of people migration, globally. Animals have been migrating globally for millennia - without passports!
Perhaps the awareness that living systems grow and develop, whereas inorganic systems age and die - entropy!
Also, when you plant a seed, you need to take care of it, and LATER you will be able to take a harvest - THINK AHEAD, AND BE RESPONSIBLE, at least for yourself!
I envisage each group CONTINUOUSLY REDESIGNING their forest gardens, as the plants grow, and the imagination and experience of the participants grows too.
ALSO, including cultural considerations - plants from people's place of origin, if they will grow in Belgium, with a protective micro-climate.
OF COURSE - there are additional social outputs, such as cooking from different cultures together.
Plants with medicinal uses can be included, fiber products are an option, EVEN a few plants "just because they are beautiful"! After some time, carving or making musical instruments from the fruit wood.
I NOTICE, that at Mouscron, the proprietors of the garden do not bother to make conserves, jams or alcohol or other products of their garden - they always have fresh food to eat, throughout the year - so they prefer to give away excess produce to their neighbours.
Also at Mouscron, they have developed a seed exchange system, various courses, and many other social aspects. Currently, they are looking to implement systems to deal with the fact that they are getting old and will die one day - but the garden and social relations could live on.
It's very well done.
At present, I am trying to create a "turn key solution", i.e. all the information and contacts that you need for anyone to do it themselves.
I am developing 2 web sites, one focused on Laeken, perhaps Jette too (communes in Brussels - there are 19 in all). The other focused on anywhere, but mostly somewhere within Brussels, or maybe in Belgium
There is a LOT of information on the net about forest gardens, in Holland, France, the UK, the USA, Australia, Costa Rica, and elsewhere - sometimes places with very different climates than here, so different plants, BUT THE DESIGN PRINCIPLES REMAIN THE SAME.
However, the balance of outputs preferred may change from forest garden to forest garden - someone likes more nuts, others like more edible vegetables, salads and flowers, others focus more on a more insect, bird, and other wildlife friendly space - You can even focus on lower fruit trees for small people, i.e. children, wheel chair users, etc.
It all depends!