What a seamless carousel is
A seamless carousel is one wide image cut into slides that line up when people swipe. The first slide ends exactly where the second begins, so the photo looks like one long scene that continues off the screen. It works well for panoramas, product line-ups, timelines and before-and-after pairs.
How the splitter cuts your image
You choose the number of slides and their shape. The splitter puts that many slides side by side, fits the strip over the centre of your image and cuts it into equal slices. Every slice has the same whole number of pixels, so no line or gap shows between slides. When your image is wider or taller than the strip, the edges are cropped and the splitter tells you how much.
Getting a sharp result
Instagram keeps feed images at most 1080 pixels wide. For three portrait slides, start from an image at least 3240 pixels wide and 1350 high; for five square slides, 5400 by 1080. Smaller images still work, but the slides are enlarged and the splitter warns you.
Post it in one go
Add the slides to one carousel in the order you downloaded them. With PostBoost you can schedule the carousel to Instagram alongside your other networks, and check it before it goes out.