I am not at all an expert in this kind of thing but it worked very well so I share it with you here.
It cost me less than £10 to make.
You will need:
Lots of good quality wood (i.e. strong enough to hold the weight of plant pots and not rotting)
The usual tools like a saw, hammer, plane, screwdriver
Nails and screws
Step 1: The design
I decided to set the shelves in a step fashion so that none would be deprived of sunlight. Note how they come forward as they go down.
It had to be made shorter than this because the longest pieces I had were 2.16m which was still a good size.
The drinks bottles at the one end you see are optional extras that can be attached to grow more plants in.
The 80cm extension at the base it to provide it with stability, in case of winds from behind but it is very open and is unlikely to happen but it's always good to take precautions.