As mentioned above, Resourcinol glue (2-part) is great for gluing teak (but you need to clamp it). It also is brown, so sort of matches the teak color. Epoxy is a good glue too, but you need to add a thickener and not just use the resin by itself. West System is fine, but you should also use 404 which is a high density filler, or 406 which is also a good filler additive or 407 low-density filler and I like this selection because the red brown color matches the teak color better. I also advise that you spline the teak pieces with a thin piece of teak that will insert into the edge of both pieces that you wish to glue together and not just glue them together (butt the pieces without the spline). This will assure that they will not separate. The other suggestion is that if you are using teak board (not plywood), that you should also have end pieces with the grain going a different way (like a 2 inch border on the ends/sides) as that will make sure your boards will not buckle or cup down the road. So, if you were gluing two boards together to make one, you should have 4 pieces of wood in total.
