We used a plastic box that held rolls, a cardboard egg carton, and potting soil (free sample - woo!)
|Fully hydrated and ready for planing.|
At planting time, the egg carton should break apart easily. Being wet all this time will make it come apart really easily. I routinely compost these and they are non-existent within days. You could also let the soil dry out some and plant them as little soil plugs - without the carton.