Abstract: Packaging bags are produced by cutting a larger material sheet into individual portions and folding each of these individual pieces to form a main body having a front wall, a back wall, side walls which stand up from a flat bottom. A lid for closing the upper opening is uniformly sloped upward from the front wall to the back wall. A ridge is formed, extending upward from the back wall, for sealing the bag closed. A trapezoidally folded flap extends upward from the back wall and is folded forward over the seal ridge. A pair of fastening tapes is used to keep the flap detachably attached to the seal ridge such that the bag, after it is once opened, can be closed again. Instead of the fastening tapes, an elongated member serving like a belt loop may be used to keep the flap retractably inserted under it to keep the flap closed.