Rake up as many dry leaves as you can. If you don't have a backyard or many trees, offer to rake a friend's yard in exchange for keeping the leaves.
Place as many leaves as will fit into a large plastic bin that has a lid. A clean industrial trash can works well, as does a large plastic storage bin.
Stir and push the leaves around in the bin with a long, wooden broom handle. Crush and pulverize them into the smallest pieces you can. If the leaves are very dry, this should happen relatively quickly.
Add 1 gallon of water to the leaves and stir until the leaves are all thoroughly wet.
Snap the container lid into place and let the leaves sit for about four weeks. Open the container and stir the leaves each week to distribute the mold and heat evenly.