I would suggest pink or blue extruded foam for your base on a 1x4 frame,
using clear silicone to hold the track down. Lay a line of silicone down where
your track will go. Lay your track onto the silicone & let it harden. You can trim
off any silicone that shows & hide it when you ballast the track. No worry about
nails, track can be easily removed if you change your layout.