How to create/compile a “proto”assembler only through binary ?

Assume a basic x86 PC (or if it is impossible due to locked access/firmware blobs etc assume the closest modern equivalent of a PC e.g an open RISC system with cpu ram hardrive and a way to interface with a keyboard mouse and a VGA/HDMI monitor)

NO OS is present.

input could be serial/parallel port keyboard floppy CDROM or even more low level ways e.g pads/jatags on the CPU/mobo if needed/applicable)

How would it be possible to enter raw binary (ones and zeroes) to it in order to compile a basic assembler for it from scratch without using any existing programming languages including existing assembly languages.