A flexible, stackable container for storing a quantity of a product may include a sealed package formed from a single sheet of film and retaining the quantity of the product disposed therein, and a lid fitment attached to a first side of the package. The first side of the package may have an outer first surface of the film and outwardly extending first corner seals formed in the film at the edges of the first side and surrounding the first side of the package. The package may also have a second side disposed opposite the first side and outwardly extending second corner seals formed in the film at the edges of the second side and surrounding the second side of the package. The lid fitment may include a base having a central opening and a lid having a complimentary shape to the base to form a seal therebetween when the lid is closed down onto the base. The base may be sealed to one of the first surface of the first side, to the first corner seals surrounding the first side, or to both, such that a portion of the first surface is accessible from the exterior of the container when the lid is separated from the base of the lid fitment.