How do I plane the top of a bench consisting of different boards and directions?

I am in the process of making a wooden bench. The top plane is comprised of multiple strips of wood glued together which I will then adhere to the rails and legs with hardware. The strips of wood aren’t flush and therefore need to be planed. Would you suggest sending it through an automatic planer or doing this sort of thing by hand given that he grains go in different directions in order to combat warppage? Thoughts?