Note: A 10 x 10 foot square of space for your Three Sisters garden is the minimum area needed to ensure good corn pollination. If you have a small garden, you can plant fewer mounds, but be aware that you may not get good full corn ears as a result.
I have planted 3 sisters grids a half dozen times. Great results but takes up a lot of square feet. It is smart farming. Corn benefits from nitrogen nodules on bean roots, squash shades soil and attracts pollinators. The ground shading acts like a living mulch to retain moisture. Layout spacing and timing of when elements are planted matter greatly. A cluster of corn seed get planted in a 10-12’ circle 4’ apart first. This establishes the planned spacing . When corn sprouts and to 4” tall thin the circle to 3-4” apart(they support each other with intertwined roots.) plant squash ( small amended mound between ) when corn grows to 10-12” plants pole beans around corn. Keep it all watered regularly. Enjoy the harvest.