A sealant mold for sealing a dome element particularly at a lower region about an interface with a substrate such as an aircraft fuel tank wall. The sealant mold is formed from a lightweight plastic material, and includes an outer cap portion having an opening formed therein, in combination with an integral outer skirt to define a gap or trough for receiving and supporting a metered quantity of a curable sealant material. The mold is slidably fitted onto a dome element with outer skirt displaced downwardly to extrude the sealant material about the lower region of the dome element. The sealant material is allowed to cure, after which the sealant mold can be stripped from the cured sealant material.