Electric knifes are used when there are more than a few fish to be cleaned and often are gifts to fishermen, so are even used for just a few fish.  The use of an electric knife will yield good results if you understand the differences in its use over a traditional filleting knife.

The first cut is the same deliberate vertical cut at the head. The next cut is one long horizontal cut to remove the fillet following the skeleton towards the tail.
Some leave the fillet attached to the fish and using the fish body as a handle remove the skin.  Either way is fine. However, in any case the ribs are left in the fillet and need to be removed.  

In using the Fillet King the key is to keep the electric knife at a low angle so that the tip of the electric knife does not poke into one of the squares. The use of a carving deck for the rib removal step is an aid for electric knife users who have an issue with keeping the anlge low. This provides a flat surface with no squares to deal with in rib removal.

Bear in mind that electic knives do not fillet as precise as a normal fillet knife where the flesh is removed by going over the rib bones in one process. This is based on our experience in filleting contests where electric knives are allowed. We have not observed a single electric knife user place in the top 25% of contests when competing against a person using a standard fillet knife.

However, where volume of fish to fillet is the object, electric fillet knives are useful and work fine on the Fillet King fillet board system.