Just an update:
After a lot of twisting in the wind, I decided to go with an organic bonsai soil slurry in a very shallow dish, the spores on top, and a clear plastic container as a "ceiling" to promote humidity. About a week and a half in and, shockingly, it seems to be growing really well for its stage. Good bits of greenery here and there, and it's still got about a month to go before it should be at full-force.
If it continues well, I'll post pictures soon. Thanks to all who helped out along the way!