This was a weekend project I built as a test for a larger raised bed in the spring.
The styrofoam box came from some steaks we ordered on line and is just over one foot cubed on the inside. I cut a piece of 4″ drain pipe, available at Home Depot, 10′ @ $7. I used some scrap pvc pipe, and cut a wedge in one end of the filler tube for unrestricted water flow.
The drain tube runs through the top/side of the tube and through the box. I wrapped the tube with weedguard cloth, filled with compost and garden soil, and planted with nine swiss chard plants. Wicking action keeps plants watered for extended periods.
Hope this gives some of you some ideas for your spring projects.