A dam for substantially laterally confining a quantity of encapsulant material over a region of a substrate, such as an interposer. The dam is configured to protrude upwardly from a surface of the interposer or other substrate. The interposer may be positioned at least partially around a slot or aperture through the substrate so as to laterally confine encapsulant material over the slot or aperture and over any intermediate conductive elements extending through the slot or aperture. The dam may be fabricated by stereolithography. A package including the interposer, the dam, and a semiconductor die to which the interposer is secured may include a sealing element between the interposer and the active surface of the die. All or part of the sealing element may also be fabricated using stereolithography. Methods and systems using machine vision in conjunction with stereolithography equipment are also disclosed.