Inputs
You'll need the URL of a specific Slack channel.
It looks like this https://app.slack.com/client/YOUR_TEAM_ID/YOUR_CHANNEL
An example here:
This is not our actual team ID and channel; it's just an example.
Parameters
You can choose to maximize the number of members to extract by setting the maximum results.
By default it is set to 10 and max to 10000.
If you want/need to extract more people, you should segment your search into smaller batch.
To use this setting with the API, you can pass max_results to the input_parameters field.