Please place the items facing the opposite direction from each other per each layer.
"Please place the items"＝「商品を置いて下さい」
"facing the opposite direction from each other"＝「お互い反対の方向に面しているように」
"per each layer"＝「一段ごとに」
Sentence in context:
"We can't have the items facing the same direction for all the layers. The products for each of the layers must be facing the opposite direction from each other, like this."
アメリカ合衆国 
