As adjectives the difference between flaskless and flashless
is that flaskless is (engineering) without a flask (container for holding a casting mold) while flashless is (of a camera) not fitted with a flash.
flaskless
English
Adjective
(-)
(engineering) Without a flask (container for holding a casting mold). flashless
English
Adjective
(-)
(of a camera) Not fitted with a flash.