The advent of additive technologies has led to a shift in the design paradigm. Manufacturability concerns regarding shape are now less critical, and within certain limits, they are not considered in the geometric design process. An exemplary case is lattice structures, where numerous repetitions of a reference cell are used as "bricks" to construct the desired final structure. While the macro shape is determined by the distribution of these bricks, the unit cell dictates the structural properties at the local (micro) level. Oftentimes, to optimize the stiffness-to-weight ratio, the reference cell is composed of structural elements such as beams or shells. In the latter case, the surface can be implicitly constructed through a level-set function. This level-set function depends on Euclidean coordinates, with the surface of interest defined as the set of points where the level-set is constant and equal to a specific value. Given the complexity of these geometries, it is advantageous to retain their implicit definition, thus avoiding the need to reparameterize them as standard multipatch surfaces, each based on two auxiliary curvilinear coordinates. In this way, the approximation space can rely on a unique reference system for the entire domain. In this contribution, we employ the Trace FEM method to study shell-based unit cells for lattice structures, providing insights into how the challenges arising from using a 3D approximation space for an inherently 2D domain are addressed. Preliminary results demonstrate the potential of this approach.