a board tray , a method for manufacturing a board tray and a tray blank from which the board tray is manufactured , said board tray containing side walls and a bottom wall made of a board layer provided on at least one surface thereof with a plastic coating , wherein areas of reduced thickness are formed in the board layer whereby portions of the plastic layer which have been melted and are disposed adjacent to areas of reduced thickness are compressed into such areas forming double - folded linear plastic compressions which seal on themselves .