for an above ground garden, containers work well. out on the web, there are guides as to what size container a certain plant needs in order to thrive. if you are wanting a platform garden, its elevated to a certain height and is aprox. 12 inches deep.
Are you talking about a raised garden bed? If so, it could be made very simply. You decide how big you want it and then you build a box frame, no bottom and no top. You lay the frame on the ground where you want it, put in landscape cloth and make sure it comes up the sides of the box, fill the box with preferably top soil because it's been screened and cleaned of rocks and debris, put your plants in that you want to grow and enjoy the bounty of your endeavors.
This should help: https://www.youtube.com/results?search_query=above+ground+garden+diy
Hello! Here are some links for how to construct a raise garden bed that might be helpful. Current pressure-treated wood is available for sale now -are safe for a raised bed vegtable garden use.
Comprehensive raised bed gardening article is informative for all gardeners (to include seniors)
Here’s how we built ours: https://www.frugalfamilytimes.com/2013/05/how-to-build-raised-garden-bed-boxes.html :)
One of my gardening books suggested using the decorative grocery bags that you buy at the grocery store. Using my old ones I just filled them with good soil and planted them with strawberries, zucchini, pumpkins, cucumbers, and flowers. At the end of the year I just dump the dirt into my garden and throw away the bags. Works great. You can move them around to the best sun spots while they are little. They are colorful and the extra water runs out the bottom. Easy to use the right amount of fertilizer and helps keep the bugs from the plant. Works good on apartment balconies too, I'd imagine.