People can't sit directly across from one another.
People have to sit at an angle across from one another.
ーPeople have to sit staggered.
「交互に座らなければいけない。」
sit staggered で「交互に・ジグザグに座る」という言い方です。
ーPeople can't sit directly across from one another.
「向かい合わせに座ることができない。」
sit directly across from one another で「向かい合わせに座る」
ーPeople have to sit at an angle across from one another.
「斜め向かいに座らなければいけない。」
sit an angle across from one another で「斜め向かいに座る」
ご参考まで!