The ??? is a workshop.
It is unlocked at Level ??
The first ??? costs ??? coins. You can have up to six of them. Each additional one costs keys. They can be upgraded.
Please see the article on workshops for information about upgrading and buying additional ones.
The table below shows the level that you get the recipe, the required materials, and the time to craft one.
This information is current as of Version 3.9.370