Growing mushrooms on sawdust blocks are the best way to grow consistent crops of a wide variety of gourmet and medicinal fungi. It is a more advanced method than growing on straw or preparing logs and requires some extra equipment and experience, but it will also open the doors to a wider range of options in terms of species that you can grow.
How to fruit: Remove the bag from the block entirely. Shiitake is fruited as a 'naked' block. It can be beneficial to flip the block upside down when you place it in the fruiting chamber. More fruits tend to form on the bottom of the block (when it was incubated) so flipping it makes these fruits come out on the top.