Abstract: The subject of this disclosure is a method for manufacturing a footwear article comprising providing of a first knitted tubular part comprising at least one fusible portion, at least one sole part, at least one flattening opening of unitary knitted construction with the first knitted tubular part and extending at least in the sole part, and providing one or more functional components, disposing, at least partly, the first tubular part substantially flat using the flattening opening; functionalizing the first knitted tubular part, at least partly, substantially flat with one or more functional components to form a footwear assembly; and transforming the footwear assembly on a preform having the foot shape in an upper, transforming the footwear assembly comprising thermoforming the footwear assembly to follow the foot shape of the preform.