Alma 43:27

And it came to pass, that Moroni caused that his army should be secreted in the valley which was near the bank of the river Sidon, which was on the west of the river Sidon, in the wilderness.

Moroni had his army hide in the valley near the river Sidon. They were on the west side of the river in the wilderness.

Moroni hid his army in a valley near the west bank of the Sidon River, in the wilderness.