A method for blocking an optical lens (100) on a holding unit (200) thanks to a thermoplastic material layer (310) comprising the steps of: a) providing around the holding unit (200) a removable part (500) comprising an upper part surface (510) which is arranged so as to extend the upper assembling surface (210) of the holding unit and not to contact the bottom lens surface (120); b) providing a predetermined volume of a thermoplastic material; c) orientating the lens (100) in a desired spatial configuration; d) positioning the lens (100) contacting the thermoplastic material of step b) at a soften or melted state and pressing the lens (100) so as to keep the lens spatial configuration constant and to let the thermoplastic material flow from the upper assembling surface (210) of the holding unit to at least a part of the upper part surface (510) of the removable part (500); e) removing the removable part.