Mold bottom for the manufacture by blow molding of a container that has a bottom that is equipped with a seat, with this mold bottom including a unit that has a molding face bearing the at least partial impression of the bottom of the container, with a pressure-release air vent being formed in the unit and emptying out, via an inner opening, on the molding face and, via an outer opening, into a pipe for exposure to air, with this mold bottom also including an insert that is provided with at least one projection housed in the air vent and that has a terminal face bearing the impression of at least one part of the seat of the container, with this insert being provided with an inner circuit for heat regulation of the projection and being mounted to move in relation to the unit.