Shaving off wood in 4"x4" to fit ez base?
The best option in hand tooling is a wide rasp. However given the eye-popping price of quality hand tools and the wide availability of cheap power tools either an electric router or hand held belt sander make reasonable alternatives.

If you need to take off more than millimeters the time honored approach is to make a bunch of cross cuts with a circular saw set to a shallow depth, then knock off the resulting "fins" with a chisel.