Collapsible enclosure having foldable side flaps and a non-foldable bottom portion

An enclosure comprising a back portion, a front portion including a back-foldable section, side flaps, and a flat uncreased bottom interconnecting said back portion with said back-foldable section of said front portion, each of said side flaps comprising a bottom side tongue and an end piece between the respective side flap and bottom side tongue, each of said side flaps further comprising a number of longitudinal fold lines, said enclosure further comprising a first cross-crease between said bottom portion and said back portion, a second cross-crease between said bottom portion and said back-foldable section, and a third cross-crease forming a back-folding precrease extending between said back-foldable section and said front portion and through said side flaps to form an intersection with each of said longitudinal fold lines at a right angle thereby hinging said end pieces to the respective side flap, said longitudinal fold lines having in each side flap one fold line longer than the other longitudinal fold lines to form two longer fold lines extending through said end pieces and through said bottom side tongues respectively, each of said longer fold lines forming a main intersection with said third cross-crease forming said back-folding precrease, each of said end piece comprising two angular precreases extending from said main intersection through the respective end piece to opposite ends of the respective bottom side tongue, whereby all of said precreases and all of said fold lines cooperate for folding said back-foldable section onto said front portion and said bottom side tongues between said uncreased bottom and said back-foldable section in an empty condition of said enclosure, and so that said enclosure can be laid flat when empty while providing an enclosure space between said front portion and said back portion when filled, said enclosure space having a width corresponding to a width of said uncreased bottom portion.