The detachment regime presents a promising reduction of the heat flux reaching the divertor plates by dissipating most of the upstream heat flux to the neutral particles. In order to access detached regimes, a sufficiently high neutral pressure in the divertor has to be ensured, which can be achieved through increasing the divertor closure. Modeling the boundary plasma and neutral dynamics while accounting for a realistic first wall geometry is thus important. The boundary region is typically studied with fluid models which are less computationally demanding than their kinetic counterparts. Spatial discretization often relies on flux-aligned grids in order to correctly resolve the anisotropic parallel transport, which comes at the cost of simplifications to the treatment of boundary conditions, e.g. by using immersed boundary conditions. In this work, the extension of GBS to handle flexible first wall geometry is described. This capability is enabled by use of curvilinear structured finite differences to allow for an accurate treatment of the boundary conditions. Grid generation and optimization leverage a spline elliptic grid generation framework originally developed in the context of isogeometric analysis applications. The first simulations of baffled TCV simulations are compared to equivalent Cartesian domain cases.