Two problems look similar but are not the same. The first is getting the slides inside one carousel in the right order. The second is getting a multi-part series (part 1, part 2, part 3, each its own post) to go out in the right order on the right days. Most schedulers handle the first reasonably well. The second is where calendars quietly go wrong: a post gets moved, a slot gets skipped, and part 3 lands on your feed before part 2.

This guide covers both, plus the platform limits that trip people up.

Part one: carousels

Know the limits before you design

A carousel is one post with several images or videos that people swipe through. The details differ by platform:

  • Instagram lets you post longer carousels in the app, but scheduling tools publish through Meta's API, which takes fewer items. Plan for 10 slides or fewer if you schedule.
  • The first slide sets the shape. On Instagram, every slide in a carousel is shown at the first slide's aspect ratio, and the others are cropped to match. Design all slides at the same size, usually 4:5 (1080 × 1350) or 1:1 (1080 × 1080).
  • Auto-posting needs a professional account. Scheduled Instagram posts go out automatically only for Business or Creator accounts.
  • Bluesky takes up to 4 images per post, and each image must be under 2 MB.
  • Pinterest, TikTok and YouTube treat multi-image posts differently or not at all, so a carousel planned for Instagram often needs a separate version there.

Name your files so the order cannot slip

The single most useful habit is boring: number the files. Use leading zeros so the order sorts correctly everywhere: 01-cover.jpg, 02-problem.jpg, 03-step-one.jpg, rather than 1, 2, 10, which some systems sort as 1, 10, 2. When you drop a folder into a scheduler, the slides should arrive already in order.

Write the carousel as a story, slide by slide

A carousel works when each slide earns the next swipe. A reliable structure for a 6 to 8 slide educational carousel:

  1. Cover: a specific promise. "4 ways to date a vintage Levi's jacket" beats "Vintage tips".
  2. The problem or context in one sentence.
  3. One idea per slide, with a short headline and a line or two of detail.
  4. A recap slide listing the ideas.
  5. A call to action: save this, follow for part 2, shop the link in bio.

Keep text large. People read carousels on a phone, often with the sound off and their thumb already moving.

Number the slides

"1 OF 6" in a corner tells people how much is left and makes them more likely to finish. It also helps you catch an out-of-order slide before it posts.

Part two: series that must go out in order

A series is a set of separate posts that only make sense in sequence: a three-part tutorial, a "decade of the week" run, a story told over five days, chapters of a launch. Each part is its own post, often on its own day.

Why series break

Calendars treat posts as independent. That is usually what you want, but it means nothing stops you, a teammate or an auto-fill feature from:

  • dragging part 3 to Monday because Monday looked empty,
  • filling a gap with part 2 while part 1 is still waiting for an image,
  • rescheduling one part after a failed post without moving the rest,
  • posting part 1 to Instagram and Threads but part 2 only to Instagram.

Followers then meet the middle of a story with no beginning.

A manual system that works

If your tool has no idea what a series is, you can still keep order with discipline:

  1. Book series first, before anything else in the week, so filler cannot take their slots.
  2. Put the part number in the caption, "Part 2 of 3", and a short "Catch up on part 1" line.
  3. Space parts evenly, on the same weekday each week or at the same time on consecutive days, so followers learn when the next one lands.
  4. Use the same channels for every part.
  5. Check the order after any change. If you move one part, look at all of them.

What it looks like when the scheduler knows

Social Snagger treats a series as its own thing. Files named B1, B2, B3, "1 of 3", "part 2" or "slide 2" are grouped into a series automatically; numbered collections are suggested rather than assumed. Each series carries its own rules: spacing between parts, a weekday, which channels, caption numbering ("1/3", "Part 1" or "Name · 1 of 3"), a hashtag set and footer, and what to do if a part fails (hold the rest, or carry on).

Then the app enforces the order:

  • Fill never places a part ahead of the part before it, on any channel.
  • Moving posts cannot put part 3 ahead of part 2. The app tells you instead of letting it happen.
  • At posting time, a part whose earlier part has not gone out is held, not posted. If you use the free Telegram bot, it messages you with Post it anyway and Skip buttons, and the hold lifts on its own once the earlier part is out.
  • The Series view shows each series with its parts in order, the state of every part, and problems such as a later part booked while an earlier one is missing.

You can also turn a whole series into one carousel with a click, or select several posts and make them a carousel. Carousels post as one post to Instagram, Threads, Facebook (photos), Bluesky (up to 4) and Tumblr, and arrive in Telegram as one album, in order. Pinterest, TikTok and YouTube skip them.

Planning the grid around a series

On Instagram, the profile grid shows newest first, top left. A three-part series posted in order ends up with part 3 first on the grid and part 1 last. That is usually fine, because people meet the series in their feed, not on your grid. If you want the series to read left to right on the grid, post it as one carousel instead, or design the three tiles so they work in either direction.

A grid preview helps here. Later, Planoly and Sprout Social (Professional and up) all show your upcoming grid; Social Snagger's Grid view does too, with out-of-order series shown in red and drag-to-swap between booked tiles.

A checklist before you schedule

  • All slides share one aspect ratio, sized for the first slide.
  • Files are numbered with leading zeros.
  • No more than 10 slides if you schedule to Instagram.
  • Text is readable on a phone.
  • Series parts have numbers in the caption and the same channels.
  • Series are booked before filler.
  • You looked at the grid and the series order after the last change.

For a wider planning routine, see how to batch a month of posts in an afternoon. If you are launching a book, the 25-post book launch plan uses series and carousels throughout.

Try it

If you have ever watched part 3 go out first, download Social Snagger. It is free for Mac, and it will not let that happen again.