The M100 is not really designed for low speed operation, but it is possible to get it running a bit better at low RPM. You can use an ESC with field oriented control (FOC) drive, which will have greater startup torque and much smoother and slower low RPM operation. FOV ESCs do need to be finely tuned specifically to the motor being used, so it would take some firmware tweaking.
Another option is a gimbal controller, which would operate the motor like a gimbal. However, I would not recommend using this specific one, as it is designed specifically for low current gimbal motors, and will overheat extremely quickly driving an M100. Something more powerful could work.
I know you would like to avoid it, but the best option really is a high ratio gearbox, given the higher speed design of the M100. This is how servos operate, they typically have a small very high RPM motor driving a set or gears with a large reduction.