Abstract: A structure including a sheet of material bent along bend lines to form a plurality of walls defining an interior volume having a predetermined cross-section. A fold-out tab portion in one of the walls has a peripheral shape complementary to the predetermined cross-section. At least one side of the tab engages an immediately adjacent, corresponding wall thereby defining the predetermined cross-section. The structure may include a bend line defining a first portion and a second portion of the sheet of material, each portion including a pre-formed bend angle flange. The pre-formed bend of the first portion is aligned with the pre-formed bend of the second portion. A section of the first portion may also overlap a section of the second portion thereby forming a multiple-sheet-thick framework. An oven housing with sidewalls, a top and a back, and a removable bottom adjustably disposed within the oven compartment is also disclosed.