Hi Carey
The original poster glued two 2" foam 4x8 sheets of rigid foam . Then Painted the base White , He did a great job.
I am like you I want a Fall to Winter layout ! Like the original poster , I plan to glue two sheets of rigid foam together . I will paint one side Green & one side White . the 4 " edge will get painted Black.
The track will not be attached to the foam . I may Lionel track sometimes & HO Track the other times .
The buildings will not be glued either .
For You , you could paint the green side Brown or Gray for your Halloween side . Then for Christmas you could sprinkle the white powder Woodland Scenics stuff on the White side.
For Me For Fall , I would use Fall colored Trees . For Me The White side , I would do the same as yours , Plus use White colored trees for Winter/Christmas .
So Carey , let me know some of your ideas . Please
Bill in Wauwatosa .