Find a place the sells Baltic Birch ply for your next table. I buy the large 5x5 sheets that have been stored flat. There are so many layers set cross grain that warping is not going on. Some woodworking shops sell pre cut pieces, but I've found those are seldom really flat. There is also an American brand that is good called Applewood ply. Look it up to find a local dealer. It comes in larger sheets. I like a double layer of premium ply, but you still need to seal the edges. Putting a top layer on it to make it slick is nice, but you can just wax it and buff the heck out of it.