What is the correct order to begin a match?

According to the official Tournament Rules and RiftJudge FAQs, the sequence to begin a match is as follows:

1. Sideboard: Players may exchange cards between their main deck and sideboard.
2. Legend: Players select and reveal their Legend.
3. Chosen Champion: Players select and reveal their Chosen Champion.
4. Battlefield: Players choose and reveal their Battlefields simultaneously.
5. Turn Order: The starting player (or the loser of the previous game in a Bo3 match) chooses whether to go first or last.
6. Draw/Mulligan: Players draw their initial hand of 4 cards and perform any mulligans.

Important Nuances:

• Simultaneous Reveals: To prevent counter-picking, all reveals (Legend, Champion, and Battlefields) must be done by placing them face-down first and revealing them simultaneously.
• Bo3 Starting Player: For the first game, the starting player is determined by an agreed-upon random method (or designated player rules in high-level play). For subsequent games in a match, the loser of the previous game chooses who goes first or last.
• Timing: This process occurs after sideboarding but before drawing the initial hand of 4 cards.