A liquid dispenser. The dispenser includes reversible modular components to define selective removability and rearrangement between them and a base structure such that one or more sheets of a passing liquid-receiving substrate may receive such liquid through interchangeable liquid-dispensing orientations. The removability features include tool-free operation to facilitate quick insertion and removal of the modular components that include at least a liquid-dispensing valve assembly and a seal that is selectively engageable with the valve assembly to protect liquid-dispensing nozzles of the valve assembly from becoming clogged with residual dried liquid during periods of inactivity of the liquid dispenser. Selective movable cooperation or attachment between the modules—as well as between the modules and the base structure—facilitates flexible configurations of the dispenser, including top-down and bottom-up liquid-dispensing orientations.