Abstract: A method for forming a shell type body (100) of self-reinforced composite thermoplastic polymer material from a plate-like element (10, 60), with a central region (11) and a peripheral region (12) surrounding said central region (11), comprises: providing a press (1) including a first and a second die portion (3, 4) which can be moved between a forming configuration, wherein they are pressed against one another, and a release configuration (Y), wherein they are spaced apart; at least one from the first and/or the second die portion (3, 4) being provided with ribs (5) on an operating face (3A, 4A) thereof intended to abut the plate-like element (10); arranging the plate-like element (10) on the press so that the central region (11) abuts on the operating face (4a) of the second die portion (4), retaining the plate-like element (10) at the peripheral region (12), moving the first (3) and/or the second die portion (4) towards the forming configuration until the first die portion (3) abuts the plate-like element