Abstract: For assembling mail items, a type of envelope is selected from different types. Another station is accordingly set and a flat object is packaged in an envelope of the selected type. Prior to the assembly of a series of mail items, a set of basic finishing instructions applying to the series is activated. This set contains a first and a second set of instructions, each for selecting a first respectively second one of the different types of envelopes and with an instruction for an associated first respectively second setting of the other station, and a selection criterion for selecting, per individual mail item, one of the sets of instructions. Thus, within the framework of a preset set of basic finishing instructions, another one of the available types of envelope can simply be selected per mail item to be assembled individually.