Answer

In the Name of Allah, Most Gracious, Most Merciful. 

All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.

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In this fatwa:

1- While standing in Prayer, one should basically place his right hand over his left forearm.

2- Scholars have different views as to where to place both hands. Most reports from the Prophet recommend placing both hands on the chest.

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Answering your question about placing hands in prayer, Dr. Muhammad Salama, PhD, Islamic Studies in English, Associate Professor at the Faculty of Islamic Sciences al-Madinah International University (Mediu), states: 

While standing in Prayer, one should basically place his right hand over his left forearm. Sahl ibn Sad, one of the Prophet Muhammad’s Companions, is reported to have said, “People were commanded that a man should place his right hand over his left forearm in Prayer.” (Al-Bukhari)

Authentic reports that describe the Prayer of Prophet Muhammad (peace be upon him) prove that he used to place his right hand over the left one. The majority of scholars, thus, consider this as one of the recommendable acts in Prayer.

Nevertheless, scholars have different views as to where to place both hands- above or below the belly button or on the chest?

Each of the three positions finds favor with a group of jurists who support their opinion with a report attributed to the Messenger of Allah.

But all the reports in this regard proved to be of doubtful authenticity, though the collectivity of the reports that attest to placing both hands on the chest gives this opinion more weight over the others.

Almighty Allah knows best.