Dihedral is never (or at least I have never encoutnered it) cut into the wing. Mostly, when you build the wing, the Rib at the root of the wing is installed at the angle of the dihedral (many kits come with a dihedral guage that you use to set the angle of the root rib). The wing joining mechanism is also set with the dihedral in mind. The wing tubes are angled to match the dihedral if the wings slot on to wing rods. If the wing is permanently joined, there is often a plywood wing-joining brace that has the dihedral cut into it.

Bascially, once the wing dihedral is set (at wing building time), there is little you can do to change it afterwards. You can't just cut it to be different (without also designing a new wing joining structure).

gus