We are planning to have our first planting trial in early August and first public planting in late August. To do this, we need to produce enough oyster castle blocks in time. We have been building wooden forms in which to pour the concrete. In case you might want to try this yourself, the following are pics that show the process.
using 2"x8" treated wood and deck screws
small blocks to create notches
exterior secured to small blocks
with deck screws
attach plywood base
surfaces painted with primer