Method for preparing a sterilised ready-meal package, comprising the steps of: providing (100) a main container defining a main volume intended to accommodate a main food product, and having a first opening at the upper part surrounded by a first planar edge; providing (200) at least one secondary container defining a secondary volume and having a second opening at the upper part surrounded by a second planar edge; introducing (300) said secondary container inside the main container, so that said first edge and said second edge are flush; introducing (400) at least one secondary food product inside the secondary volume; introducing (500) at least one main food product inside the main volume; making (600), by means of a first sealing head facing the first edge, a perimetric seal between a covering film, arranged to cover said first and second opening (2b; 2b', 3b; 3b'), and said first edge; making (700), by means of a second sealing head facing the second edge and physically distinct from the first sealing head, an inner seal between the covering film and the second edge.