Once I establish the track centerline, I glue cork roadbed down centered on the centerline. I use slow-cure ZAP-GAP. I put a bead of ZAP-GAP on the plywood and spray ZIP-KICKER on the underside of the cork. CAREFULLY place the cork onto the plywood. You only get one shot! When the ZIP-KICKER meets the ZAP-GAP it sets up instantly! I use a similar method to secure track to the cork. I spray the cork with the ZIP-KICKER and put a small bead of ZAP-GAP on the underside of three end ties and then about every 5 or 6 ties for the length of the flex-track. CAREFULLY place the track on the cork, again, because you only get one try!
My layout is in the basement and to date I haven’t had any trouble with shifting due to temperature or humidity. I do get some heat because the furnace is next to the layout and I use a de-humidifier during the summer.
The draw-back is that this method is very permanent! To change track requires a lot of scraping and a bit of a mess. The flex-track is salvageable but the cork is a loss.
Also remember to check if your model railway layout is available and check if it fits your usage
