He always leaves his clothes on his bedroom floor.
この場合、to leave one's ... で「脱ぎっぱなし」を表現します。
ーHe always leaves his shoes in the front entrance.
「彼はいつ玄関に靴を脱ぎっぱなしにする」
to leave his shoes で「靴を脱ぎっぱなしにする」
ーHe always leaves his clothes on his bedroom floor.
「彼はいつも寝室の床に服を脱ぎっぱなしにする」
to leave his clothes で「服を脱ぎっぱなしにする」
ご参考まで！
カナダ 
