It would work similar to the current garden pot: requires soil and water, allows you to plant the same stuff you can garden now. It would be a liftable object (maybe the size of a long bench), and it would allow you to plant 3 of the same plant in it (e.g. 3 dandelions).
It would save you some space and most importantly allow you to garden in a more efficient way by cutting down the amount of pots you have to refill daily. It might also allow you to use slightly less materials, so instead of 4 soil per plant, you only need 2 or 3.
Last but not least, it would also make for some nice decorative item
