In this paper, we propose a highly efficient scheme, SLICE (a scalable and low stretch routing scheme), enabling greedy routing for wireless sensor networks (WSNs) deployed in complex-connected 3-D settings, whose topologies are often theoretically modeled as high genus 3-D WSNs. Compared to previous 3-D greedy embedding techniques, SLICE improves both the robustness and applicability. 1) It achieves a smaller distance distortion and a lower routing stretch with guaranteed delivery. While it follows the basic idea to embed the surface network to a planar topology to enable greedy routing, the embedding method proposed in SLICE is novel. We first slice the surface network to a genus-0 open surface with exactly one boundary. Then, to achieve a lower distance distortion, we purposely propose a variation of the Ricci flow algorithm, by which this open surface is flattened not to a planar annulus, but to a planar convex polygon, resulting in a lower routing stretch. 2) This is the first work, to the best of our knowledge, that enables greedy routing in high genus 3-D WSNs with general topologies. SLICE not only works for high genus 3-D surface WSNs, but also can be easily adapted to more general cases: high genus 3-D surface networks with holes, and high genus 3-D volume networks. For a high genus 3-D surface network with holes, SLICE embeds it to a planar convex polygon with circular holes, where our proposed greedy routing variation can be applied. For a high genus 3-D volume network, SLICE embeds the inner nodes to a height structure attached to the convex polygon, and a variation of greedy routing scheme with guaranteed delivery is proposed in this structure. The effectiveness of SLICE is validated by extensive simulations.