Yes that's true. No wood needed you just heap the soil/compost up into a long, flat topped heap (imagine you've just dug a grave
) I've got a couple of them and they work fine. You can always edge them with something as you get it
Bricks, breeze blocks, etc, it doesn't have to be wood
I have some Link-a-Bord beds which have been given to me on various birthdays etc and I love them as they need no painting (ever) and are maintenance free. I collected mine to save postage, as the place is near me. (see Armillatox, Morton, Derbyshire) I can put them together myself too with just a bit of wood and a hammer
My husband and I worked it out buying the wood, nails, etc treatment and they worked out roughly the same