I can give exact measurements if you want, but the substrate is coco coir, vermiculite, and gypsum, supplemented with some blood meal, (ironically) oyster meal, bat shit, coffee grounds, and some random cardboard scraps for structure.

Still honing in the oysters because I’m new to growing this type of mushroom! But so far I’ve found that minimal air flow helps a ton. In my little indoor greenhouse I accidentally had the fan off for a few days and then this honker popped up. So next round I’m doing only 10-15 minutes of fan per day. Maybe even less