This thesis presents the collimating system for a Lloyd-Materwave-Interferometer with very cold neutrons. The system met its demands and is part of the beam preparation setup to collimate the VCN-beam at the Institut Laue Langevin. Moreover it is especially used to select the beam position with the highest count rate for a given wavelength and divergence. The beam preparation consists of motor-driven neutron-optic elements like supermirrors, monochromating supermirrors, boron-steel slits and shielding material enriched with boron. Furthermore, the thesis explains the electronic control and the necessary automatisation of the motorized components with LabVIEW. The software was programmed in a modular and error suppressing way, thus serving as a basis for the integration of further devices. Data from the measurements to optimize the position within the beam during the beamtime 2015 are described and elaborately explained. In particular, reflections on the inner side of the slits are discussed as well as the impact of the monochromating supermirrors on the angular distribution of the beam. One finds that those mirrors do not change the preparation of the angular distribution in a measurable way. After the complete beam preparation, including the monochromating mirrors, the mean flux over the angle and the area of the slit is (3,63+/-0,36)*10^-3 cps/(mm^2 *mrad), while the beam spread angle is (3,30\pm0,08) mrad. Possible concepts to develop a new slit system are analyzed. It is shown that tilting the sides of a slit with respect to each other is useful to avoid reflections. The thesis concludes with the discussion of a possible realization of the entrance slit of the interferometer.