I’m using a piece of rubber shelf liner (like ‘Grip-It’ on Amazon) between tabletop and each A&A board. Stuff is like $1 a roll at the grocery store. Slight dampening affect and definitely keeps things from sliding around.
Yes, as long as it is a named island. Island’s without names are not playable spaces in the game and cannot be used for anything, even landing your own planes, troops etc.