An assembling device (1) for manufacturing a panel assembly, which includes at least two tooling systems (2, 3) and a tooling controller communicatively coupled to the tooling systems and programmed to instruct the tooling systems to operate on one or more wooden slats so that, if the length of a wooden slat (101) exceeds a predetermined threshold, the wooden slat gripping means grip the wooden slat at different parts, and are moved relatively to each other in order to align their centerlines and to correct the straightness (S 101 ) of the wooden slat.