With the recent integration of Non Terrestrial Networks (NTNs) into 3GPP Release 17, 5G networks are expected to benefit from the NTN large coverage area. This integration will help mobile terrestrial networks reach a worldwide coverage. However, this ultimate ubiquity also comes with its set of challenges to overcome. One of the main issues is the seamless integration of NTNs into the existing mobile network standard. In this paper, we propose a comprehensive architecture integrating NTNs as slice-aware backhaul links. This architecture remains fully compliant with the 3GPP standard. For this purpose, we propose an end-to-end slice model integrating NTNs and 5G networks. Then, we implement this model on a 5G-satellite testbed, adding new functional components to interconnect both networks at the control and data plane levels. Lastly, we evaluate the performances of our method using the aforementioned testbed by monitoring each slice and their related Quality of Service requirements.