Generously beveling the inside edge corners of these tabs will help guide the upper stage into place. The remaining insulation sacks are then spiraled around into place until the well is filled. The well box should be constructed as tightly as possible, but any slight gap between it and the lid is desirable in order to permit a small amount of air exchange. If you've done too good a construction job, a small diameter nail can be placed between box and lid to provide this gap. A small hatch in the center of the lid is handy for when it is only necessary to have access to the duct for monitoring or adjusting conditions.
Monitoring is done by installing a small thermometer and hygrometer attached to an old broom handle.
The neck is perfectly shaped for attaching a cord. Tying each end of a double length creates a convenient handle and balances the jug. In mild winters these same containers can be installed frozen to lower the inside temperature. Another desiccating material, silica gel, available at craft shops, although more expensive initially, can be reconditioned again and again by slow oven drying. These sacks can be weighted with a fist size stone to aid installation.