>>31553100This was all explained in a Japanese GS guide book that Nintendo published.
Eggs are made from materials similar to nests, such as sticks, mud, grass, whatever. The newly born Pokemon is placed inside like an incubator, so the parents can carry it around and keep it safe until it's grown enough.
The Pokemon will only give birth and make the egg while humans aren't watching. Prof. Elm and his assistants have tried to observe the act, but every time the egg would appear while he fell asleep or went the bathroom or something. So it's literally true that Daycare workers didn't see the egg be made, no matter how ridiculous that it.
