This is an excellent application that will help you to easily split your Instagram photos into 9 squares. 

Grid Photo Maker for Instagram 9 Grid Giant Square is easy to use and will work for all your photos. The app also offers you the option to create square photos or crop images. 

In addition, you can choose to add effects to your images such as stickers, frames, filters, and more. 

The process will not take much of your time. All you have to do is to select the photos you want to add to your posts, choose the grid you want to use, crop the pictures, and you are ready to go.