In order to use the method, you need to be familiar with memory palaces. See this post if you are not.
Building the Koine Greek Square of Stops PalaceFirst, choose a rectangular room to use as your memory palace. You are going to be breaking up the room into a three by three grid. Perhaps you could just use the classroom in which you learned or are learning Greek.
In the front left hand corner of the room, imagine that there is a pig. Make the pig interact with something in that corner of the room. If there isn't anything there, perhaps you could imagine the pig is wallowing in a bucket of slop that's in the corner.
Now in the front center of the room, imagine a bear. If you are using your Greek classroom, it might work well to imagine that the bear is substituting for your Greek teacher.
In the front right hand corner of the classroom imagine a flamingo. Maybe he is standing on one leg trying (and failing miserably) to climb up the wall.
Now, above the pig, bear, and flamingo, imagine that there is a giant cage stretching across the front of the classroom. The cage hangs down from the ceiling, and it's filled with pandas.
As always with memory palaces, make sure you can clearly see all of this. Make it real in your mind.
Now, in the middle part of the room on the far left side, imagine a kangeroo. Imagine the kangeroo doing something ridiculous.
In the very center of the room, imagine a goose waddling around in circles, suddenly, a viper lurches down from the ceiling and tries to grab the goose.
Still in the middle part of the classroom, imagine in the far right a random group of camels. Once again, see these camels doing something ridiculous. Maybe they just came in the room after tearing down the wall and are looking for something to drink.
Finally, at the back of the classroom in the left corner, imagine a tiger. See the tiger interacting with that corner of the room in whatever way you like.
At the back of the classroom in the middle there is a dalmatian, barking in agreement at the great teaching.
Lastly, in the back right corner there is a turtle. Once again, make the turtle interact with that corner of the room in some memorable way.
An Explanation of the Koine Greek Square of Stops PalaceAs I explained in this post on learning the order of the alphabet, the pig is pi, the bear is beta, the flamingo is phi, the kangeroo is kappa, the goose is gamma, the camel is chi, the tiger is tau, the dalmatian is delta, and the turtle is theta (to keep from thinking that the turtle could be tau, notice that a turtle is shaped like the letter theta). Also, the panda is psi (the pig goes with pi because pi and pig start with the same two letters), and the viper is xi.
Note that the psi and xi are the letters that you get when you add a sigma to the rows of letters that the panda and viper are above (e.g., so if you add a sigma to a pi, you get a psi, and if you add a sigma to a chi, you get a xi). You may find it helpful to add more animals or other objects to your palace in order to help you remember other rules related to the square of stops.
Now that you've placed all the animals in the room, look back through your room again and make sure you can picture everything. If you can, then you've successfully memorized the square of stops— and I can assure you of this: you will remember the square of stops much longer using this method than if you had learned it by rote!