I would assume a substrate of moist, hardwood sawdust would be all that's needed for rearing the larvae, probably doesn't even need to be rotten sawdust. Burying some dog food or some equivalent is recommended since longhorn larvae seem to like a little protein sometimes, and they are also cannibalistic I hear.
I once got Prionus californicus to oviposit on crushed rotten cottonwood, and even sand, so I don't think Prioninae females tend to be very picky about egg laying sites. Could be wrong though.