It may sound difficult but its as easy as mixing a little Brown rice flour with vermiculite and water. then you cook that, inject the jar with spores and wait.
thats literally all there is to it. the spores do the rest.
the only thing you have to pay attention to is the humidity (perlite will keep it plenty humid) and the heat.
P. cube are the easist to grow. the more sterile you can make the environment the better but once the jars are colonized the Mycelium is pretty tough.