Preheat the oven to 180 degrees Fahrenheit.
Collect containers that are going to be used for the soil sterilization. Fill containers with 4 inches of garden or potting soil. Smooth the surface of the soil so it is even in the containers.
Cover each container with aluminum foil. Crimp the edges of the foil all the way so a tight seal is formed.
Poke a meat thermometer through the foil into the soil in the center of the container.
Once the oven has reached 180 degrees, place containers in the oven.
Heat soil until it reaches 180 degrees. Once this temperature is reached, time the soil for 30 minutes.
Turn off the oven and open the door. Let containers completely cool before removing them from the oven.
Store soil in the containers until it's needed or remove it from the containers and place it in plastic, sealable bags that have been labeled.