Try Loctite PL300 10 fl. oz. Foamboard VOC Adhesive ... At - Home Depot. It works for me.

Just for the record so people don't confuse materials and their properties: "Styrofoam" is the proprietary trade name for extruded polystyrene blue foam by Dow. A comparable product is the pink "Foamular" by Owens-Corning. There are also other extruded foam insulations by other manufacturers, such as those of polyurethane. The extruded foams are of a uniform structure comprised of tiny closed cells and are stronger, denser, easier to cut precisely and work with and more resistant to water and moisture vapor penetration than the ubiquitous white "bead board."

The white stuff is usually cheap bead board that is molded, not extruded, and comprised of small, soft beads. When cut, it has a tendency to crumble into large and small chunks of beads. Its properties do not match those listed above for extruded foams.

Unfortunately, "Styrofoam" has become the name associated with all foams, but it ain't so. If you get bead board, don't think you have the properties of Styrofoam.

Dante 

Sorry to have offended you sir -- I humbly make a correction and an apology to you sir - I am using the white beaded board that my daughter gave me - You are quite right sir it is cheap - My daughter didn't charge me anything for it - But I thought it might workout for the better considering that every local company (that installs insulation) and lumber-yard in my area which sells the blue extruded polystyrene board by Dow and/or the pink Foamular board by Owens-Corning all insist upon thinking it is made of "Gold" and insists upon selling it at the price of $44.00 to $50.00 per 4 foot by 8 foot sheet - Considering I'm Retire and my income consists of a fixed income of a "Social Security" check I thought the blue and pink foam boards were a little out of my reach and still be able to make ends meet for my household - Once again Sir, My Humble apologies - I didn't think a commonly used name was going to create such a havoc with a simple question which was just to simply ask someone's opinion about how and what I needed to use to hold this white beaded foam board down to my bench-work and also the track and the other accessories to the foam board whether it be "Elmers (white or Yellow) Glue", "Liquid Nails", "long screws with Large Washers", or what-ever?

Thank you for your suggestion about using lock-tite it is a great product as you state - but for my purpose at only 10 oz per bottle it might be a little too expensive for the amount that I might (or will) possibly need considering I have a fairly large bench-work layout to cover with the foam-board (2 ft (24 inches) wide by 52 feet (624 inches) long) - but I will keep it in mind and get a bottle for use for smaller things that I will be doing on my layout.

If you are on a cheap budget as I am sometimes, check out Dollorama for glues, and I believe - in fact I know - they sell foam glue to attach foam to stuff and stuff to foam, I bought some but never used it.  But all my glues just about are from there as well as other things I use for the layout.  The foam glue will cost you $1.25.

The 30" flex track and the rigid straight and curved track, called snap track, should work together no problem. I have no clue as to the other types of track you mentioned. The 3 1/2" foam could work well for scenery but I, myself would not use it for a track base.

My reply back to the rail fan casenundra - Thank you for the advice - Instead of gluing the plastic snap track and flex track directly to the white foam board, which you don't recommend  - Now here is a possible alternate scenario, which I would appreciate your's, or anyone else's thoughts on the subject - If I first mounted the track to 1/4" thick pieces of wall paneling, (or 1/4" or 1/2" ) plywood or to masonite strips, then grooved out a trough (a roadbed hollow so that the height of the bottom of the plastic snap-track would be level with the top of the white foam) and then inlaid and glued that down into the hollowed out roadbed groove of the white foam, would that be sufficient for mounting down the track to the white foam?

Thank you for your advice - Yes I'm on a low budget fixed income (Retired) - unfortunately in the towns near me there is no Dollarama stores (at least not within a hundred miles one way), even the nearest Home Depot or Lowe's is at least 40 miles away (80 round tip) - I'm hoping to be able to maybe use Elmer's white or yellow glue which I can buy by the gallon or maybe a 5 gallon bucket of contact cement (it's going to take several gallons to do the whole layout bench work and foam - The two main reason's I'm trying to use white foam is (1) it is free from my daughter - (2) I'm building my layout inside an older model single axle RV travel trailer and I need to keep the weight down for my 1/2 ton ford pickup to be able to haul - Because my usual methods of building a layout with drywall mud covered newspapers over chicken wire and wood framework I'm afraid, would be too heavy for my pickup to haul any distance beyond a few miles.

For you mountains, check out light weight spackle.

I have used a lot of EPS (Expanded Polystyrene) on my layout. White or Yellow PVA work just fine with it.