A buck system for forming and framing an opening in a poured concrete foundation includes a plurality of buck sections matching the desired dimension of an opening. Each of the buck sections is affixed to an adjacent buck section forming a closed geometric shape. Each buck section has an inner surface defining an inside dimension of the opening and each of the buck sections has a first channel and a second channel. The first channel snuggly accepts an edge of a first insulated concrete foundation wall of the insulated concrete foundation walls and the second channel snuggly accepts an edge of a second insulated concrete foundation wall of the insulated concrete foundation walls.