I've written up some details on the design/build here with info on the assembly and such. A 3-site planter for 1.5" rockwool cubes. I designed it for an 'indoor garden' project I've been tinkering on. This planter is intended mainly for herbs, but I may also use them for early growth stages of larger plants in the future. In between the rockwool holders is an open area intended to be filled with expanded clay pellets (or other inert moisture retainer), and there are three integrated locating features for positioning moisture sensors in the hydroton.