All-Spin Logic (ASL) devices provide a promising spintronics-based alternative for Boolean logic implementations in the post-Complementary Metal-Oxide Semiconductor (CMOS) era. In principle, any logic functionality can be implemented in ASL. In practice, the performance of an ASL gate is significantly affected by layout choices, but such implications have not been adequately explored in the past. This article proposes a systematic approach for building standard cells in ASL, which are a basic building block in an overall design methodology for implementing large ASL-based circuits. We first propose a new technique to reduce the magnet count for an ASL majority gate but still ensure correct functioning through layout optimization methods. Building on physics-based analysis, we then build a standard cell library with diverse functionality and characterize the library for delay, energy, and area. We perform delay-optimized technology mapping on ISCAS85 benchmark circuits using our library. Our approach results in circuits that are 12.90% faster, consume 26.16% less energy, and are 33.56% more area efficient compared to a standard cell library that does not incorporate layout-based optimization techniques of our work.