I normally see them growing directly on dead elms. The larger the pores on the bottom, the more mature the shroom and supposedly the worse tasting.
I’ve tried fresh ones and older ones and they all suck. Good to be able to identify in a life or death situation, but I’ll look at them and maybe take a picture and keep walking, and stop at the gas station on the way home and get some peanuts and beef jerky instead of wasting time cooking what tastes like fried rubber.