Splitting an image sounds simple, cut it into equal pieces, but getting a clean result depends on matching the split mode to what the pieces will actually be used for. A grid split divides both width and height, which is exactly right for an Instagram profile puzzle where the pieces sit in a square tile layout, but it is the wrong choice for a carousel post, where every slide should be the full height of the original photo. Columns mode solves that by only slicing along the width, producing tall slides rather than small squares.
The crop shape setting exists because most source photos are not perfectly square, and a grid split treats width and height independently. Splitting a 4000 by 3000 pixel photo into a 3 by 3 grid without cropping first produces pieces that are wider than they are tall, which looks stretched or mismatched once posted individually. Choosing the Square crop shape center-crops the photo to a 1 to 1 ratio before any slicing happens, so every one of the nine resulting pieces is genuinely square.
Getting the posting order right for a feed puzzle
A 3 by 3 Instagram grid puzzle only works if the pieces are posted in the correct order, since a profile feed fills from the bottom right and reads backward. The pieces in this tool are numbered 1 to 9 reading left to right and top to bottom, which matches how you would read the original photo, but posting to Instagram requires reversing that order, piece 9 first, then working down to piece 1 last. The number badge on each downloaded piece and each preview tile is there specifically so this order is easy to track no matter how many pieces are involved.
For a carousel post, order matters just as much but works the opposite way. Carousel slides post in the same left to right order the pieces are numbered here, so piece 1 becomes the first slide a follower sees when they open the post, and piece 5 (or whatever the last piece is) becomes the final slide at the end of the swipe.
Choosing a piece count
More pieces means a more detailed effect but also a bigger commitment, a 4 by 4 Instagram grid puzzle takes over sixteen posts on a profile rather than nine, and a ten slide carousel asks more of a follower's attention than a five slide one. For posters, the right piece count usually comes down to your printer's maximum page size and how large you want the final assembled print to be, more pieces means a bigger poster built from more individually printed pages.