The toolchain, or “flow ... the FPGA, Arachne-pnr, a place-and-route tool that turns a symbolic netlist into the physical stuff that IceStorm needs, and Yosys which synthesizes Verilog ...

While there has been no shortage of FPGA-based recreations of classic processors ... ground up and started with a 6502 implementation in Verilog. You can see in the second video below that ...