How do they determine the starting position for Fisher Random / Chess 960?

I was watching the Fischer Random World Championship with Magnus Carlsen and Wesley So, and I am wondering how they determine the starting position?

Is it software that picks, or do they start left to right, and pull pieces out of a bag? Or is it some other way?

Thank you.

I am pretty sure they have some sort of software for this

From what?

Oh so basically the software picks it

8.4.3. Drawing of positions

● Set up of the pieces will be decided by a drawing made by Fischer Random Generator software with all players present 15 minutes before the start of the first game of each time control. This setup then will be used for both games. The players will attend this drawing, and will then be given time before the start of play to confer with a second.

Found in the download here: https://www.frchess.com/regulations

Interestingly, if the classical position is picked than they pick again.

I thought software would be used; interesting to see all of the other rules surrounding it. Thank you.

The positions are numbered 1 to 960, with one of these being the standard starting position. Here are some links with information.

https://en.wikipedia.org/wiki/Fischer_Random_Chess_starting_position

https://en.wikipedia.org/wiki/Fischer_Random_Chess_numbering_scheme

https://chess960.net/start-positions/

Bishops must be on opposite color.

There must be a rook on the left and right of the king.

yup, bishops for obv reasons and rooks to allow castling

The point of chess960 is that it's impossible to memorize the starting position, so the opening must be played by opening principles, rather than memorizing opening theory, or in english, memorizing the best opening moves. 

It's called 960 because there are 960 different starting positions. 

Also, it was made by Bobby Fischer.

Quiero que me den un logro jaja

Point was, Fischer was giving serious thought to getting back into chess in the 90s. But he didn't want to learn the 25 years of theory he had fallen behind on. So he tried to change chess.