Heterogeneous, multicore SoC architectures are a critical component of today’s computing landscape. However, supporting both increasing heterogeneity and multicore execution are significant design challenges. Meanwhile, the growing RISC-V and open-source hardware (OSH) movements have resulted in an increased number of open-source RISC-V processor implementations; however, there are fewer open source SoC design platforms that integrate these processor cores. We present modifications to ESP, an open-source SoC design platform, to enable multicore execution with the RISC-V CVA6 processor. Our implementation is modular and based on standardized interfaces. These properties simplify the integration of new cores. Our modifications enable RISC-V-based SoCs designed with ESP for FPGA to boot Linux SMP and execute multithreaded applications. Coupled with ESP’s emphasis on accelerator-centric architectures, our contributions enable the seamless design of a wide range of heterogeneous, multicore SoCs.