Stance, Grips, Hands, Legs

For kouchi-gari to work, many elements must come into play seamlessly. This is true of any technique in judo.

Judo is a very technical sport. For a move to work, it requires many factors to come together seamlessly.

For example, if you want to do a kouchi-gari. You need to be clear first what stance you and your opponent have. If it's a kenka-yotsu (opposite) stance, you can do a skipping kouchi-gari. If it's an ai-yotsu (same) stance, you could consider kouchi-gake. The stance determines the version of the throw to use. You'll then need to take the appropriate grip to make this technique work. Lastly, although kouchi-gari is a leg throw, the hands are crucially important. You'll need to know what the tsurite (lapel) hand and the hikite (sleeve) hand should be doing.

It doesn't matter what classification of throw you do, whether hand throw, leg throw, hip throw or sacrifice throw, all these things come into play:
a) stance
b) grip
c) hands
d) legs

Certain variations of a throw work only in a certain stance situation. And if you don't have the right grip, it won't work. If only your hands or only your legs come into play without the other, again, it's unlikely to work. So everything has to come together seamlessly.

That's what makes judo so hard. I've heard so many beginners say judo is the hardest thing they've tried. It takes a lot of hard work over a course of a long period of time to master judo techniques. Perhaps that is why judo is not that popular. People don't have patience and tend not to stick around long enough for their techniques to work. They give up.

But for those who want to excel in judo, they need to bear in mind that it takes many different elements coming together in harmony for a technique to work.