As much as I would love to reuse old, discarded wooden shipping pallets, I am worried about some of the pressure treated wood that may contain toxins that you would then bring in to your home. I could always buy wood slats and make the planter from scratch or another option is to use other ready made wood structures like wine crates or wine holders as vertical containers.
Before hanging any vertical garden, it is best to plant the herbs with the pallet flat on the ground, then water thoroughly and leave the garden horizontal for 2 weeks. That way this will allow the roots to grow and strengthen.
For now, I need to figure out where I can place such a planter. I may have to wait until we have done some renovations to our little house, so this project will have to sit on my wishlist for now.