If the declaration expressly permits, the boundaries between or among adjoining units may be relocated by an amendment to the declaration. The owners of the units shall prepare an amendment to the declaration, including the plat, that identifies the units involved, specifies the altered boundaries of the units and their dimensions and includes the units’ identifying numbers. If the owners of the adjoining units have specified a reallocation between their units of the allocated interests, the amendment shall state the proposed reallocation in a reasonable manner. The amendment shall be executed by the owners of those units, shall contain words of conveyance between or among them and, before recording the amendment, shall be submitted to the board of directors. Unless the board of directors determines within thirty days that the proposed amendment is unreasonable, which determination shall be in writing and specifically state the reasons for disapproval, the association shall execute its approval and record the amendment.