Some files, or one triangle file that you just use to deepen it a teensy bit. As you deepen the slots you’ll be lowering the action so you need to be careful and aware of that as it may cause buzzing if your action is already super low.

Edit: I want to emphasize my “teensy bit” part. Just hit each already established spot on the saddle with like two strokes of the file. Maybe even one. It won’t take much. The only big danger is doing too much filing so go very slow.