Get some gravel from somewhere for a drainage layer, I found these on the lawn: Then add your soil, this is (gasp)from a bag. Planter soil with some compost added. Spread it out...Staple gun the edges all around: Trim the plastic and then staple again where it is gapping: I took the lettuce seedling I had planted out a month ago, some of dh's onions, and some leftover radish seeds: Separated out the lettuces and spaced them out in the drawer: Planted a row of the onion seedlings down the middle: And finally sprinkled some radish seeds all over, they can be thinned as needed: There it is all done: The radishes will be ready to eat in 3-4 weeks, more can be seeded as needed so there can be a steady supply. The onions can have their tops trimmed for green onions, they will continue to grow more and won't need reseeding. The lettuces can have the outer edge leaves snapped off for salads while the little inside leaves keep growing. All that is really needed is for a container sized tomato plant growing alongside.
I'll stick this where it will get enough sun yet not get overheated and where it will be protected from the frost. Handy this as our conditions in the yard vary as it heats up during the season. Where it will grow nicely now in the cool spring it would bake during the summer. When it does get hot I think the deck stairs on the north side of the house will be best. For right now, either on the south side of the house or even in the greenhouse will work. It is still mighty chilly overnight!
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Edited to add that the lettuce drawer could use more drainage, or a big sign that says, "Don't water me so much kids!" It doesn't look as healthy as it could.