What is the correct sequence for revealing battlefields and determining turn order at the start of a game?

Ruling: Battlefields are chosen secretly and revealed simultaneously before determining turn order. Turn order is then determined using any fair random method agreed upon by all players.

Sequence:

• Choose legends
• Choose champions
• Choose battlefields secretly and reveal them simultaneously
• Determine turn order using any fair random method
• Draw cards
• Mulligan (starting with the player who has first turn)

Nuances:

• The Proving Grounds rulebook had a different method (flipping battlefields to determine first player) but this was designed for onboarding and is not the official rule
• Using battlefield flips as the random method is valid as long as battlefields were already revealed before making that determination
• For games 2 and 3, battlefields are revealed before the loser of the previous game decides whether to go first or second