Now why are you going to inject spores into the casing, do you want to waste them?

You inject the spores into the substrate and when that is fully colonized, then you sandwhich that between the casing materiel.

At most I would leave the jars sit for three days and that is with tape on the holes.

What substrate are you using?

L

Perlite is one way to go once your cakes have been 'birthdayed'. From what I've read the cakes are best sat on something that keeps them off the perlite (e.g a jar lid) until after the first flush, then you can sit them on the perlite to get some more moisture into them to encourage further flushes. All the info you need is here in the Shroomery's grow/find section.
Cos I'm not yet speaking from personal experience. My first attempt at growing just crashed But if at first you don't succeed......

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"He who makes a beast of himself gets rid of the pain of being a man."
-Dr. Johnson
"I should play God and just shoot you myself."
-Tool
happy shrooming!