Sometimes making a rain barrel is as easy as sticking a big barrel under an eavestrough... This one had a spigot on it for easy hose attachment but for a small area, you could totally just dunk a watering can into it. The only problem with an uncovered rain barrel would be breeding mosquitoes. A fine-ish netting on top would solve that easily.
Here is Bozena's beautiful round plot too! She started it last year and this year is growing a cover crop of buckwheat. It'll be great to plant potatoes there next year because of all the extra potassium the buckwheat builds.