An option you may want to consider is using a sectional track system such as fastrack, and not attaching the track to the table, as mentioned by ACE above.
I build my layout on a flat table covered in plywood, then covered the table with carpet underpad. I painted the underpad using "earth coloured" laytex paint, with woodlands scenic coloured grass, dirt and some fine ballast (N-scale ballast) to give the layout a natural ground & grass look.
With the carpet underpad, you can run any wires under the underpad, bringing them through the underpad under the track (where ever the track may be) and connecting to the fastrack by using 0.011 connectors sized for fastrack.
Whenever I make changes to the layout, and that is quite often, I just move the track as needed, and move the buildings etc to fill the space available.
I have attached a few pictures of my layout. Let me know if you have any questions and I would be happy to provide answers, based on my learning curve over the past 18 years.
The layout with carpet underpad base, painted & textured with track. The buildings from the lower level are temporarily stored on the upper level:
Layout with buildings & scenery added. All buildings and scenery trees are placed on layout, and can be easily removed. Any building wires for lighting poke through the underpad under the building, and are connected to the building wires.
This method has helped me evolve my layout over the years, allowing me to make countless upgrades and improvements.