A simple and low-cost laser writing system that allows one to obtain micrometer features with high-quality borders is presented. After an overview of the complete fabrication process of masks to carry out the ion-exchange technique in glass in a selective way, a complete description of the experimental setup for direct laser writing is given, including details about such important parts as the control of the motorized stage and the system to perform focusing and alignment. A discussion of the way of focusing the laser beam in order to get the best performance is presented. Results of the characterization of the laser writing system and some examples of integrated optical elements and masks to fabricate them are shown.