Forming device 100 for forming a layer of containers 300 arranged as a quincunx which comprises a conveyor belt 1 configured to advance said containers 300 according to a feeding direction X of the conveyor belt 1, an equipment piece bearing a plurality of partitions 2 positioned parallel to said direction X, wherein said partitions 2 divide the upper surface of the conveyor belt 1 into a plurality of channels 3, each having a width such to allow the passage of a single row of containers 300, wherein the equipment piece further comprises a series of feeding devices configured for dosing and releasing, in a controlled manner, the containers 300 exiting from the channels 3, each placed at the outlet of each channel 3, and said equipment piece is movable according to direction Y substantially perpendicular to the feeding direction X of the conveyor belt.