a method of constructing footwear includes providing a mold having an inner cavity , injecting an expandable material into the inner cavity , removing the expandable material from the inner cavity such that the material expands to form a footwear - shaped shell having an inner cavity and at least one recessed area offset from an inner surface of the shell , and inserting a chassis within the inner cavity of the expanded shell . the chassis has one or more components adapted to protect a user &# 39 ; s foot from injury . the insertion of the chassis within the shell permanently affixes the one or more components within the at least one recessed area of the shell .