It probably would have been easier to construct if we had attached the wheels to a piece of wood (like the Pinterest photo), but since we never seem to choose the easier route, here's what we did. First, Dave constructed a planter box from scrap wood. Then he attached the first wheel to the box before filling it with soil and planting sunflowers seeds.
The tricky part was attaching the wheels together so he used a bit to drill holes in the wheels before attaching them with nuts and a screw.
And here's the final product! We painted the planter and spray painted the wheels to match so it really pops against the garage. The last step was lining the wheels with a string of lights that we attached to a timer that turns on at dusk. Cheap, beautiful and one-of-a-kind - you got to love that!