My Layout
First off I had to remove the lower section of track and roadbed and add 3 X 6 section. The second below photo shows the lower track section removed.


Below photo show the new 3' X 6' framing added on, then the 3/4" plywood is added on top.

The above photo shows the new main line cork roadbed being added. Liquid nail is used under the cork roadbed and push pins used to hold it in place till it dries. The below photo shows all the cork roadbed completed, next I start laying all the track. This is glued down using Elmer's liquid white glue.

The track in the above photo is not glued down.