Many tournament organisers strive to present a perfectly balanced battlefield for a mission, usually creating mirrored sides with the same building copied so that each player has the same terrain at the same distance as the opponent. The idea of balanced battlefields is to make a mission that does not favour either side in any way and allows players to concentrate on which makes better choices. However, the rules for setting up matched play missions, both in the core rule book and the Grand Tournament 2020 Mission Pack mention never mention balanced boards and the example battlefields vary from almost balanced to decidedly unbalanced.
The rules for setting up a battle include a rule that indicates a perfectly balanced battlefield is not the intention of the game designers. Players roll off to determine who is the defender and who is the attacker, with the defender choosing which is their deployment zone. This is an important consideration that helps balance the advantage the attacker gains from reactively placing units onto the table after the defender deploys a unit. In a perfectly balanced layout, the choice of deployment zone is meaningless, and yet the attacker has the deployment advantage.
Tournament organizers should allow a measure of imbalance in the tables. In any case, the terrain available should be close to the same amount of volume. A good rule of thumb is to shoes enough terrain to fit half the battlefield and to divide it somewhat evenly across the board as it is laid down. Be careful not to give an overt advantage in one area, such as a terrific sniper point close to one player’s deployment zone but nothing to aid snipers on the other end of the board. Stealing an idea from Star Wars Legions tournaments, organizers might consider placing the terrain next to the table and have each player set down one piece in turn until they are all on the table, with the defender placing first.