The professional way to do it is with a 1/2" router blade guided by a worktop jig with a couple of connecting bolts routed into the underside of the worktop. It depends if you have exactly a right angle and how long the two pieces are as to how easy it is.
If you've got a lot of time on your hands and you don't mind it not being perfect, you can cut it with a jigsaw.
The professional way to do it is with a 1/2" router blade guided by a worktop jig with a couple of connecting bolts routed into the underside of the worktop. It depends if you have exactly a right angle and how long the two pieces are as to how easy it is.
If you've got a lot of time on your hands and you don't mind it not being perfect, you can cut it with a jigsaw.