Stack the trays on top of the base followed by the lid. You can run the oast one of two ways. The heat source can be placed on top, such as a hair dryer. The original plans recommended a bonnet style hair dryer
set on low.
In practice it may make more sense to have the heat source underneath the oast. I have run it this way using the base of a dehydrator which heats and puts out a moderate air flow. When filled with more hops/bins, greater airflow will be required. The bins are the perfect size to fit a box fan
. I plan to dry the bulk of my harvest by placing a box fan in the lowest tray.
Even better, if you have a temperature controller you can place the probe inside the oast and cycle the heater on/off to keep the ideal temp. Home growers have reported drying hops at 95-140 F. Commercially, they are usually dried 140-170 F but with a carefully regulated air speed. The trays closest to the heat source will dry faster so rotate them out as you dry. You can use just a couple trays or stack to your heart's content, so long as you have a powerful enough heater and fan to push the air.