Mushbox's compost grow bags are can be used to fruit mushrooms directly inside the bag, or can be broken up and mixed into a casing layer. Fruiting inside the bag will produce a smaller patch of mushrooms than using a casing but it is one of the most simple methods for growing mushrooms.
All you need to do is inject the bag with LC (liquid culture) or a spore syringe and start the incubation process. There is a special patch of rye grain near the inoculation point that will help start the process, once the spores germinate you can watch the mycelium grow as it colonizes rye grain first then moves into the compost. You can also drop mycelium directly into the bag from another source instead of injection of culture or spores.
Once the bag is fully colonized it will appear fully white. Now you can fruit the mushrooms directly inside the bag, or break it up and transfer to a casing or other substrates. To fruit inside the bag all you need to do is add 12 hours of light and maintain the proper fruiting temperature for the species of mushroom your growing. You will need to open the bag and exchange the air often, the mushrooms should start pinning within 10-15 days. Once you have fully grown fruits you can pick the mushrooms and start the process again.
The video shown below is for a rye grain grow bag but the inoculation and incubation process is exactly the same for every grow bag product.