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.