Making air pruning pots / root trainers

We made plant pots which automatically prune plant roots when they hit the air. The outside wall is made of building plastic which has dents in it and is normally used for separating a cellar wall from the earth around it.
We came up with various designs and then brainstormed for the best one which needed to fit our criteria.

Setting parameters for making root trainers
some thoughts before prototyping

The pots needed to be:
– easy to assemble in an efficient production line
– made out of the available materials on farm (Richard had bought two rolls of the cellar plastic)
– 40 cm high with a diameter of 20 cm and round
– have a base that air prunes and is not sitting on the ground
– easy to take apart for planting
– cheap material cost
– moveable