This flask has been filled with the white liquid which would turns into the quickly growing block of ice. So, like an action, you can throw such flask almost up to 20 feet, which is shattering it on an impact. However it make a ranged attack which is against to a creature or an object, treating the flask like an improvised weapon.
Al though on a hit, the target would take 2d6 cold damage and even it becomes restrained gy normally growing ice if the creature is may Large or smaller. Even though the creature could be end this particular condition by using its action to make a DC 13 Strength check to break the ice. Of course any fire damage dealt to the ice ends the restrained condition immediately.