I've set up, re-set up, and refurbished ancient nurseries.... Ask Me Anything!! Under a tree I would not worry about putting them "up" on anything, I would prepare the ground with a graded gravel bed and weed fabric if you have a rampant weed problem already, if it's kind of subdued and only grows very low growing things that wouldn't grow up in to the pots I wouldn't worry about it too much.
There will be weeding!!! Try and identify which sorts of weeds are very rampant from seed, here we had a sort of spurge that was perennial, would go from seed to dropping seed in 30 days, and poisoned plants around it.
Also, try to be creative, go to garden shows with very choice plants and sell them for profit and exposure, put effort into growing the very best plants without using toxins, and look into a fertilizer injector- something like a siphonex will get you started, something like a dosatron or dosamatic will be a good long term investment. You will have to fertilize, don't kid yourself, a good analogy is a plant in a pot long-term is like a bird in a cage. Bird in wild would select whichever seed it needs and seek it out, find calcium, find grit, etc; bird in a cage needs everything it could possibly ever need brought to it. A good organic system is do-able, if you ever use chemical fertilizers, be VERY CAREFUL!!! Good results can be obtained with a careful hand and an injector, easy to get fake good results while killing the soil..... VERY VERY VERY HARD NOT TO POISON THE WATERWAYS WITH PHOSPHORUS!!! One could do this easily with organic as well, be careful! You might think of this and plant things to absorb the runoff down stream, cannas, cattails, colocasia I have used before. THINK OF THE RUNOFF, MAN!
A dream system would be to find the low spot on the property, where runoff will collect, tilt the land toward there and make a pond with fish and plants, and use the pond water for fertilizer, diluted. One could get away with planting plants in good organic soil, well drained with pumice, and a bit of rock phosphate, and watering with the pond water, using the sludge from a filter in a fertilizer injector for rapidly growing plants.