These hash channels are produced by us and we produce them daily. Hash channels are simply registered whatsapp accounts. Professional Whatsapp blasting software uses these channels (which are made up of the phone number and its related authentication hash) to blast out messages from numerous accounts all at once to bypass whatsapp's spam limitations. So when you have hundreds to thousands of hash channels, you can blast out thousands of messages to whatsapp users in any country you want.
Whatsapp hash channels look like this:
Now, to produce hashes in great numbers it requires a lot of skill and a lot of raw phone numbers that you control. And you have to know exactly how to extract the hashes. This requires specialized software to do so. But the hashes are fully ready-to-go accounts and include names and a profile picture for each account. These are added to each profile to make it harder to detect the account as a spammer.