A lot of my work went into separating the bed from the ground which is seething with hungry tree roots that have crippled most other attempts of growing vegetables. If you don't have that root problem then you could probably skip the plastic lining step and simply bury the base of the pavers in the ground. Drainage is facilitated by a layer of course sand at the bottom and 3mm or so gaps between the pavers.
Step 1: Foundation
Additional steps that I added but may not be necessary was a brick and earth foundation covered with old carpet and a thick plastic liner to stop tree roots getting into the bed.
Step 2: Building
The top frame is made of 70x35mm treated pine, and is made to hang over the edge of the pavers by 30mm. L brackets are used to hold the frame together.
My quick and dirty approach to sitting the frame onto the pavers is to use large coach screws, which stop the pavers falling over. See 3rd photo below. I figured the pavers can't fall in once the bed is full of soil. It really would be better engineering to solidly attach the frame somehow to the pavers by drilling them and maybe using L brackets and bolts. The way I've done it is working great for me but I don't have earthquakes where I live or kids climbing on it.
Step 3: Base Frame and Drainage
A step not pictured is that I filled the bottom of the bed with a well drained sandy mixture and lined the gaps between the pavers with a strip of shade mesh to stop them clogging with soil.