I’m using a “ladder” method for the roadbed.   Two strips of plastic trim from Home Depot, separated by spacers made from treated 2”x2” lumber.    The trim comes in white, so I’ve been spraying it with Krylon primer before I put it in place.

Once on the ground, I pound in some 2x2 to hold it in place, and put in some screws to make sure the track is level.

Track is code #250 (1/4” inch high) AMS flex track.  It easily bends to the roadbed, so I do not need to use a rail bender.  I fasten it down with a screw every few inches.