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I think they might mean this https://www.jigidi.com/
Basically you upload or select an image, chose number of pieces and ready to go. You post the link of the puzzle and add in the end the message with the invite only giveaway. I couldn't tell you more as I've never tried to create one but I have participated in a few and this is ho it was done.

Another one is this http://www.itstoohard.com/create in which it's closer to a quiz or an enigma. But again I have never created one.

Other than those 2 sites some create cryptography puzzles on their own or similar type of events

There is a guide. And another one.

Here is my advice: make a question where the answer is potato. Question you need to figure out yourself, look deep into your soul. Now go child!

Here are two I made years ago. Let me know if either is the type of thing you're looking for.

_____ the Load

Mystery Man

Shameless plug for my Nonogram Puzzles :)
(The thread is dead though I passed pretty much all my keys lol)

I made the generator available to everyone on my GitHub and I can also generate the puzzles myself if it seems too tedious to set up.