The invention relates to a method for manufacturing a board tray (7), to a tray blank feasible for the method, and to a tray obtained by the method. The method comprises moulding a blank of plastic-coated board into the tray (7) comprising a bottom (3), side walls (4), as well as a rim flange (5), the blank being compressed in a direction transverse to the tray's side walls and rim flange. According to the invention, the blank is made thinner on its side opposite to the plastic coating such that, during the moulding process, the plastic coating double-folds at the compressed parts and stabilizes compressions (8) by becoming sealed to itself. Making the blank thinner is most conveniently effected by carving the board layer with a laser beam for having the fiber material predominantly or completely removed from where the cuts are located. As a result of the moulding process, the tray's rim flange (5) develops a smooth plastic surface which enables closing the tray hermetically with a heat-sealed cover.