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How to grow portobello mushrooms
Build a tray frame out of scrap wood.
Pick up some scrap wood from a lumber yard or purchase boards from a home improvement store. The frame should be about 8 in (20 cm) deep and at least 6 in (15 cm) long.
Nail the wood together to form the bed. Instead of assembling a tray, purchase a mushroom-growing kit from a gardening store or online.