Maybe a little more detail is required here.

Composite wing halves are usually joined in the mold before the halves have been removed from the mold. At that point the joint edges have been trimmed and any internal structure is also in place, usually glued to the bottom skin. By internal structure I refer to spars, wing screw hard points, aileron cap strips, centre section reinforcement, etc, etc. A resin/filler bead is then applied to all edges that will contact the top skin. The mold is then closed. Only after all that has cured is the wing removed from the mold.

Ed S