Thanks very much for all replies genuinely, but you all missed the point.
The application described is not designed to slow Earth's rotation.
Instead it is converting linear momentum (Earth-moon tide) to angular momentum (through a lever, onto the sea floor thus the planet) by using force from external (moon) source to alter Earth within local reference frame (ex moon).
The result is to turn the Earth slowly over a long period, a few hours each day, pole over pole, which put another way the equator is shifted, say England might be for a time be on Earths equator.
The reason this is considered the only way an individual might do this, is because it is relatively simple to implement, energy free/self powered and requires no maintenance. Set and forget.
So for example you could affix a 4mile x 2mile sail to an A-Frame on the ocean floor. The sail will drag the lever one-way with the tide each day. The lever perhaps 1/4mile long is attached to the sail at one end, and its base to a rocky undercrop or other rigid point, where converted angular momentum adds rotational energy each day to the lever base so turning the Earth a tiny bit each day, pole over pole.