Visualizing medical images from a patient as physical 3D-models (phantom models) has potential roles in the medical field, from education to preclinical preparation and clinical research. However, current phantom models are generally generic, expensive, and time-consuming to fabricate. Thus, there is a need for a cost-and time-efficient pipeline from medical imaging to patient-specific phantom models. In this work, we present a method for creating complex 3D sacrificial molds using an off-the-shelf water-soluble resin and a low-cost desktop 3D printer. This enables us to recreate parts of the cerebral arterial tree as a full-scale flow device (10x6x4 cm) in transparent silicone rubber (polydimethylsiloxane, PDMS) from computed tomography angiography images (CTA). We analyze the channels with magnetic resonance imaging (MRI) and compare them with the original patient data. The results show good conformity and smooth surface finish for the arteries. Also, we evaluate our method by looking at its capability to reproduce 1 mm channels and sharp corners. We find that round shapes are well reproduced, whereas sharp features show some divergence. Our method can fabricate patient-specific phantom model with less than 2 hours of total labor time and at a low fabrication cost.