Posting slots are the times of week a channel should post at. Once set, Ocoya suggests them when you schedule, so you’re choosing from your plan rather than picking an hour each time.
Ocoya describes them as the weekly times this profile should use when suggesting scheduled posts from your queue.
Set them
Open Channels → ⋯ → Manage on a channel, then Posting slots. There’s also a shortcut from the post editor — Edit posting slots on a selected channel.

The Posting slots tab: a column per day, and a row at the bottom for adding a time across several days at once.
Add one time to one day
Add slot in that day’s column.
Or add the same time across several days
The row underneath — Add a new posting time for … — takes a day selection (Every Day, Weekdays, Weekends, or a single day), a time, and Add posting slot. This is the quicker route for a recurring time.
Remove any you don't want
Remove the slot from the day it sits under.
The tab header carries a count, so a 0 next to Posting slots means this channel has none set.
Slots are set per channel, so your LinkedIn schedule can differ from your Instagram one — which is usually what you want, since the audiences behave differently.
What they do and don’t do
They suggest, they don’t publish. A slot is a recommendation offered when you schedule. Setting slots does not make posts appear at those times on its own — something still has to create the post.
If you want posts to actually go out on a rhythm without you writing each one, that’s a workflow. See Create a workflow.
They’re in the brand’s time zone, like everything else scheduled. Set the time zone first or your slots will be offset. See Time zones and scheduling.
Choosing times
A few slots you’ll actually fill beat a dense grid you won’t. Start with two or three a week per channel and add more when you’re consistently ahead.
If you have analytics or knowledge of when your audience is active, use it. Otherwise start with mid-morning and early evening on weekdays, and adjust once you have a few weeks of your own data.