A cell culture vessel includes a vessel body, support columns, and a stabilizer device. The vessel body defines a cell culture chamber enclosed between a bottom wall and a top wall. The support column is within the cell culture chamber and extends between the top wall and the bottom wall. The stabilizer device covers a width and length of the cell culture chamber and has a column engaging structure that is sized to slidingly engage the support column such that the stabilizer device is movable along the support column as a liquid culture medium is received in the cell culture chamber. The support column guides the stabilizer device along a length of the support column as the stabilizer device rises with rising liquid level in the cell culture chamber during a liquid culture medium filling operation.