Structure. A dime sized hole under some is a good start. Mice , voles ect. pave the way. And offer prey.
A place to sun. A place to cool. Masonry , cement , stone/rocks thermal mass holds heat well into the night at times.
Being cold blooded, such options don't escape notice when encountered.
Water or at least moisture = prey. Even little sized prey if need be. Slugs ect..
Should be moisture near the structure your snakes are using. A short visit away.
Put my stand wood base /floor on top of the platform built last year.
No more sunning snakes on it like prior years. (I don't mind them being around , I'm not there much).
No snakes sighted the other day mowing for hours. But stuff was tall too and watching for fawns (none encountered) meant not watching to the sides for snakes on the run.
Did play don't run over the leopard frogs a couple times. So there's still bigger daytime prey for snakes.